nodeModifyTable.c

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/*-------------------------------------------------------------------------
 *
 * nodeModifyTable.c
 *    routines to handle ModifyTable nodes.
 *
 * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    src/backend/executor/nodeModifyTable.c
 *
 *-------------------------------------------------------------------------
 */
/* INTERFACE ROUTINES
 *      ExecInitModifyTable - initialize the ModifyTable node
 *      ExecModifyTable     - retrieve the next tuple from the node
 *      ExecEndModifyTable  - shut down the ModifyTable node
 *      ExecReScanModifyTable - rescan the ModifyTable node
 *
 *   NOTES
 *      The ModifyTable node receives input from its outerPlan, which is
 *      the data to insert for INSERT cases, the changed columns' new
 *      values plus row-locating info for UPDATE and MERGE cases, or just the
 *      row-locating info for DELETE cases.
 *
 *      The relation to modify can be an ordinary table, a foreign table, or a
 *      view.  If it's a view, either it has sufficient INSTEAD OF triggers or
 *      this node executes only MERGE ... DO NOTHING.  If the original MERGE
 *      targeted a view not in one of those two categories, earlier processing
 *      already pointed the ModifyTable result relation to an underlying
 *      relation of that other view.  This node does process
 *      ri_WithCheckOptions, which may have expressions from those other,
 *      automatically updatable views.
 *
 *      MERGE runs a join between the source relation and the target table.
 *      If any WHEN NOT MATCHED [BY TARGET] clauses are present, then the join
 *      is an outer join that might output tuples without a matching target
 *      tuple.  In this case, any unmatched target tuples will have NULL
 *      row-locating info, and only INSERT can be run.  But for matched target
 *      tuples, the row-locating info is used to determine the tuple to UPDATE
 *      or DELETE.  When all clauses are WHEN MATCHED or WHEN NOT MATCHED BY
 *      SOURCE, all tuples produced by the join will include a matching target
 *      tuple, so all tuples contain row-locating info.
 *
 *      If the query specifies RETURNING, then the ModifyTable returns a
 *      RETURNING tuple after completing each row insert, update, or delete.
 *      It must be called again to continue the operation.  Without RETURNING,
 *      we just loop within the node until all the work is done, then
 *      return NULL.  This avoids useless call/return overhead.
 */
 
#include "postgres.h"
 
#include "access/htup_details.h"
#include "access/tableam.h"
#include "access/tupconvert.h"
#include "access/xact.h"
#include "commands/trigger.h"
#include "executor/execPartition.h"
#include "executor/executor.h"
#include "executor/instrument.h"
#include "executor/nodeModifyTable.h"
#include "foreign/fdwapi.h"
#include "miscadmin.h"
#include "nodes/nodeFuncs.h"
#include "optimizer/optimizer.h"
#include "pgstat.h"
#include "rewrite/rewriteHandler.h"
#include "rewrite/rewriteManip.h"
#include "storage/lmgr.h"
#include "utils/builtins.h"
#include "utils/datum.h"
#include "utils/injection_point.h"
#include "utils/rangetypes.h"
#include "utils/rel.h"
#include "utils/snapmgr.h"
 
 
typedef struct MTTargetRelLookup
{
    Oid         relationOid;    /* hash key, must be first */
    int         relationIndex;  /* rel's index in resultRelInfo[] array */
} MTTargetRelLookup;
 
/*
 * Context struct for a ModifyTable operation, containing basic execution
 * state and some output variables populated by ExecUpdateAct() and
 * ExecDeleteAct() to report the result of their actions to callers.
 */
typedef struct ModifyTableContext
{
    /* Operation state */
    ModifyTableState *mtstate;
    EPQState   *epqstate;
    EState     *estate;
 
    /*
     * Slot containing tuple obtained from ModifyTable's subplan.  Used to
     * access "junk" columns that are not going to be stored.
     */
    TupleTableSlot *planSlot;
 
    /*
     * Information about the changes that were made concurrently to a tuple
     * being updated or deleted
     */
    TM_FailureData tmfd;
 
    /*
     * The tuple deleted when doing a cross-partition UPDATE with a RETURNING
     * clause that refers to OLD columns (converted to the root's tuple
     * descriptor).
     */
    TupleTableSlot *cpDeletedSlot;
 
    /*
     * The tuple projected by the INSERT's RETURNING clause, when doing a
     * cross-partition UPDATE
     */
    TupleTableSlot *cpUpdateReturningSlot;
} ModifyTableContext;
 
/*
 * Context struct containing output data specific to UPDATE operations.
 */
typedef struct UpdateContext
{
    bool        crossPartUpdate;    /* was it a cross-partition update? */
    TU_UpdateIndexes updateIndexes; /* Which index updates are required? */
 
    /*
     * Lock mode to acquire on the latest tuple version before performing
     * EvalPlanQual on it
     */
    LockTupleMode lockmode;
} UpdateContext;
 
 
static void ExecBatchInsert(ModifyTableState *mtstate,
                            ResultRelInfo *resultRelInfo,
                            TupleTableSlot **slots,
                            TupleTableSlot **planSlots,
                            int numSlots,
                            EState *estate,
                            bool canSetTag);
static void ExecPendingInserts(EState *estate);
static void ExecCrossPartitionUpdateForeignKey(ModifyTableContext *context,
                                               ResultRelInfo *sourcePartInfo,
                                               ResultRelInfo *destPartInfo,
                                               ItemPointer tupleid,
                                               TupleTableSlot *oldslot,
                                               TupleTableSlot *newslot);
static bool ExecOnConflictLockRow(ModifyTableContext *context,
                                  TupleTableSlot *existing,
                                  ItemPointer conflictTid,
                                  Relation relation,
                                  LockTupleMode lockmode,
                                  bool isUpdate);
static bool ExecOnConflictUpdate(ModifyTableContext *context,
                                 ResultRelInfo *resultRelInfo,
                                 ItemPointer conflictTid,
                                 TupleTableSlot *excludedSlot,
                                 bool canSetTag,
                                 TupleTableSlot **returning);
static bool ExecOnConflictSelect(ModifyTableContext *context,
                                 ResultRelInfo *resultRelInfo,
                                 ItemPointer conflictTid,
                                 TupleTableSlot *excludedSlot,
                                 bool canSetTag,
                                 TupleTableSlot **returning);
static void ExecForPortionOfLeftovers(ModifyTableContext *context,
                                      EState *estate,
                                      ResultRelInfo *resultRelInfo,
                                      ItemPointer tupleid);
static TupleTableSlot *ExecPrepareTupleRouting(ModifyTableState *mtstate,
                                               EState *estate,
                                               PartitionTupleRouting *proute,
                                               ResultRelInfo *targetRelInfo,
                                               TupleTableSlot *slot,
                                               ResultRelInfo **partRelInfo);
 
static TupleTableSlot *ExecMerge(ModifyTableContext *context,
                                 ResultRelInfo *resultRelInfo,
                                 ItemPointer tupleid,
                                 HeapTuple oldtuple,
                                 bool canSetTag);
static void ExecInitMerge(ModifyTableState *mtstate, EState *estate);
static TupleTableSlot *ExecMergeMatched(ModifyTableContext *context,
                                        ResultRelInfo *resultRelInfo,
                                        ItemPointer tupleid,
                                        HeapTuple oldtuple,
                                        bool canSetTag,
                                        bool *matched);
static TupleTableSlot *ExecMergeNotMatched(ModifyTableContext *context,
                                           ResultRelInfo *resultRelInfo,
                                           bool canSetTag);
static void ExecSetupTransitionCaptureState(ModifyTableState *mtstate, EState *estate);
static void fireBSTriggers(ModifyTableState *node);
static void fireASTriggers(ModifyTableState *node);
 
 
/*
 * Verify that the tuples to be produced by INSERT match the
 * target relation's rowtype
 *
 * We do this to guard against stale plans.  If plan invalidation is
 * functioning properly then we should never get a failure here, but better
 * safe than sorry.  Note that this is called after we have obtained lock
 * on the target rel, so the rowtype can't change underneath us.
 *
 * The plan output is represented by its targetlist, because that makes
 * handling the dropped-column case easier.
 *
 * We used to use this for UPDATE as well, but now the equivalent checks
 * are done in ExecBuildUpdateProjection.
 */
static void
ExecCheckPlanOutput(Relation resultRel, List *targetList)
{
    TupleDesc   resultDesc = RelationGetDescr(resultRel);
    int         attno = 0;
    ListCell   *lc;
 
    foreach(lc, targetList)
    {
        TargetEntry *tle = (TargetEntry *) lfirst(lc);
        Form_pg_attribute attr;
 
        Assert(!tle->resjunk);  /* caller removed junk items already */
 
        if (attno >= resultDesc->natts)
            ereport(ERROR,
                    (errcode(ERRCODE_DATATYPE_MISMATCH),
                     errmsg("table row type and query-specified row type do not match"),
                     errdetail("Query has too many columns.")));
        attr = TupleDescAttr(resultDesc, attno);
        attno++;
 
        /*
         * Special cases here should match planner's expand_insert_targetlist.
         */
        if (attr->attisdropped)
        {
            /*
             * For a dropped column, we can't check atttypid (it's likely 0).
             * In any case the planner has most likely inserted an INT4 null.
             * What we insist on is just *some* NULL constant.
             */
            if (!IsA(tle->expr, Const) ||
                !((Const *) tle->expr)->constisnull)
                ereport(ERROR,
                        (errcode(ERRCODE_DATATYPE_MISMATCH),
                         errmsg("table row type and query-specified row type do not match"),
                         errdetail("Query provides a value for a dropped column at ordinal position %d.",
                                   attno)));
        }
        else if (attr->attgenerated)
        {
            /*
             * For a generated column, the planner will have inserted a null
             * of the column's base type (to avoid possibly failing on domain
             * not-null constraints).  It doesn't seem worth insisting on that
             * exact type though, since a null value is type-independent.  As
             * above, just insist on *some* NULL constant.
             */
            if (!IsA(tle->expr, Const) ||
                !((Const *) tle->expr)->constisnull)
                ereport(ERROR,
                        (errcode(ERRCODE_DATATYPE_MISMATCH),
                         errmsg("table row type and query-specified row type do not match"),
                         errdetail("Query provides a value for a generated column at ordinal position %d.",
                                   attno)));
        }
        else
        {
            /* Normal case: demand type match */
            if (exprType((Node *) tle->expr) != attr->atttypid)
                ereport(ERROR,
                        (errcode(ERRCODE_DATATYPE_MISMATCH),
                         errmsg("table row type and query-specified row type do not match"),
                         errdetail("Table has type %s at ordinal position %d, but query expects %s.",
                                   format_type_be(attr->atttypid),
                                   attno,
                                   format_type_be(exprType((Node *) tle->expr)))));
        }
    }
    if (attno != resultDesc->natts)
        ereport(ERROR,
                (errcode(ERRCODE_DATATYPE_MISMATCH),
                 errmsg("table row type and query-specified row type do not match"),
                 errdetail("Query has too few columns.")));
}
 
/*
 * ExecProcessReturning --- evaluate a RETURNING list
 *
 * context: context for the ModifyTable operation
 * resultRelInfo: current result rel
 * isDelete: true if the operation/merge action is a DELETE
 * oldSlot: slot holding old tuple deleted or updated
 * newSlot: slot holding new tuple inserted or updated
 * planSlot: slot holding tuple returned by top subplan node
 *
 * Note: If oldSlot and newSlot are NULL, the FDW should have already provided
 * econtext's scan tuple and its old & new tuples are not needed (FDW direct-
 * modify is disabled if the RETURNING list refers to any OLD/NEW values).
 *
 * Note: For the SELECT path of INSERT ... ON CONFLICT DO SELECT, oldSlot and
 * newSlot are both the existing tuple, since it's not changed.
 *
 * Returns a slot holding the result tuple
 */
static TupleTableSlot *
ExecProcessReturning(ModifyTableContext *context,
                     ResultRelInfo *resultRelInfo,
                     bool isDelete,
                     TupleTableSlot *oldSlot,
                     TupleTableSlot *newSlot,
                     TupleTableSlot *planSlot)
{
    EState     *estate = context->estate;
    ProjectionInfo *projectReturning = resultRelInfo->ri_projectReturning;
    ExprContext *econtext = projectReturning->pi_exprContext;
 
    /* Make tuple and any needed join variables available to ExecProject */
    if (isDelete)
    {
        /* return old tuple by default */
        if (oldSlot)
            econtext->ecxt_scantuple = oldSlot;
    }
    else
    {
        /* return new tuple by default */
        if (newSlot)
            econtext->ecxt_scantuple = newSlot;
    }
    econtext->ecxt_outertuple = planSlot;
 
    /* Make old/new tuples available to ExecProject, if required */
    if (oldSlot)
        econtext->ecxt_oldtuple = oldSlot;
    else if (projectReturning->pi_state.flags & EEO_FLAG_HAS_OLD)
        econtext->ecxt_oldtuple = ExecGetAllNullSlot(estate, resultRelInfo);
    else
        econtext->ecxt_oldtuple = NULL; /* No references to OLD columns */
 
    if (newSlot)
        econtext->ecxt_newtuple = newSlot;
    else if (projectReturning->pi_state.flags & EEO_FLAG_HAS_NEW)
        econtext->ecxt_newtuple = ExecGetAllNullSlot(estate, resultRelInfo);
    else
        econtext->ecxt_newtuple = NULL; /* No references to NEW columns */
 
    /*
     * Tell ExecProject whether or not the OLD/NEW rows actually exist.  This
     * information is required to evaluate ReturningExpr nodes and also in
     * ExecEvalSysVar() and ExecEvalWholeRowVar().
     */
    if (oldSlot == NULL)
        projectReturning->pi_state.flags |= EEO_FLAG_OLD_IS_NULL;
    else
        projectReturning->pi_state.flags &= ~EEO_FLAG_OLD_IS_NULL;
 
    if (newSlot == NULL)
        projectReturning->pi_state.flags |= EEO_FLAG_NEW_IS_NULL;
    else
        projectReturning->pi_state.flags &= ~EEO_FLAG_NEW_IS_NULL;
 
    /* Compute the RETURNING expressions */
    return ExecProject(projectReturning);
}
 
/*
 * ExecCheckTupleVisible -- verify tuple is visible
 *
 * It would not be consistent with guarantees of the higher isolation levels to
 * proceed with avoiding insertion (taking speculative insertion's alternative
 * path) on the basis of another tuple that is not visible to MVCC snapshot.
 * Check for the need to raise a serialization failure, and do so as necessary.
 */
static void
ExecCheckTupleVisible(EState *estate,
                      Relation rel,
                      TupleTableSlot *slot)
{
    if (!IsolationUsesXactSnapshot())
        return;
 
    if (!table_tuple_satisfies_snapshot(rel, slot, estate->es_snapshot))
    {
        Datum       xminDatum;
        TransactionId xmin;
        bool        isnull;
 
        xminDatum = slot_getsysattr(slot, MinTransactionIdAttributeNumber, &isnull);
        Assert(!isnull);
        xmin = DatumGetTransactionId(xminDatum);
 
        /*
         * We should not raise a serialization failure if the conflict is
         * against a tuple inserted by our own transaction, even if it's not
         * visible to our snapshot.  (This would happen, for example, if
         * conflicting keys are proposed for insertion in a single command.)
         */
        if (!TransactionIdIsCurrentTransactionId(xmin))
            ereport(ERROR,
                    (errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
                     errmsg("could not serialize access due to concurrent update")));
    }
}
 
/*
 * ExecCheckTIDVisible -- convenience variant of ExecCheckTupleVisible()
 */
static void
ExecCheckTIDVisible(EState *estate,
                    ResultRelInfo *relinfo,
                    ItemPointer tid,
                    TupleTableSlot *tempSlot)
{
    Relation    rel = relinfo->ri_RelationDesc;
 
    /* Redundantly check isolation level */
    if (!IsolationUsesXactSnapshot())
        return;
 
    if (!table_tuple_fetch_row_version(rel, tid, SnapshotAny, tempSlot))
        elog(ERROR, "failed to fetch conflicting tuple for ON CONFLICT");
    ExecCheckTupleVisible(estate, rel, tempSlot);
    ExecClearTuple(tempSlot);
}
 
/*
 * Initialize generated columns handling for a tuple
 *
 * This fills the resultRelInfo's ri_GeneratedExprsI/ri_NumGeneratedNeededI or
 * ri_GeneratedExprsU/ri_NumGeneratedNeededU fields, depending on cmdtype.
 * This is used only for stored generated columns.
 *
 * If cmdType == CMD_UPDATE, the ri_extraUpdatedCols field is filled too.
 * This is used by both stored and virtual generated columns.
 *
 * Note: usually, a given query would need only one of ri_GeneratedExprsI and
 * ri_GeneratedExprsU per result rel; but MERGE can need both, and so can
 * cross-partition UPDATEs, since a partition might be the target of both
 * UPDATE and INSERT actions.
 */
void
ExecInitGenerated(ResultRelInfo *resultRelInfo,
                  EState *estate,
                  CmdType cmdtype)
{
    Relation    rel = resultRelInfo->ri_RelationDesc;
    TupleDesc   tupdesc = RelationGetDescr(rel);
    int         natts = tupdesc->natts;
    ExprState **ri_GeneratedExprs;
    int         ri_NumGeneratedNeeded;
    Bitmapset  *updatedCols;
    MemoryContext oldContext;
 
    /* Nothing to do if no generated columns */
    if (!(tupdesc->constr && (tupdesc->constr->has_generated_stored || tupdesc->constr->has_generated_virtual)))
        return;
 
    /*
     * In an UPDATE, we can skip computing any generated columns that do not
     * depend on any UPDATE target column.  But if there is a BEFORE ROW
     * UPDATE trigger, we cannot skip because the trigger might change more
     * columns.
     */
    if (cmdtype == CMD_UPDATE &&
        !(rel->trigdesc && rel->trigdesc->trig_update_before_row))
        updatedCols = ExecGetUpdatedCols(resultRelInfo, estate);
    else
        updatedCols = NULL;
 
    /*
     * Make sure these data structures are built in the per-query memory
     * context so they'll survive throughout the query.
     */
    oldContext = MemoryContextSwitchTo(estate->es_query_cxt);
 
    ri_GeneratedExprs = (ExprState **) palloc0(natts * sizeof(ExprState *));
    ri_NumGeneratedNeeded = 0;
 
    for (int i = 0; i < natts; i++)
    {
        char        attgenerated = TupleDescAttr(tupdesc, i)->attgenerated;
 
        if (attgenerated)
        {
            Expr       *expr;
 
            /* Fetch the GENERATED AS expression tree */
            expr = (Expr *) build_column_default(rel, i + 1);
            if (expr == NULL)
                elog(ERROR, "no generation expression found for column number %d of table \"%s\"",
                     i + 1, RelationGetRelationName(rel));
 
            /*
             * If it's an update with a known set of update target columns,
             * see if we can skip the computation.
             */
            if (updatedCols)
            {
                Bitmapset  *attrs_used = NULL;
 
                pull_varattnos((Node *) expr, 1, &attrs_used);
 
                if (!bms_overlap(updatedCols, attrs_used))
                    continue;   /* need not update this column */
            }
 
            /* No luck, so prepare the expression for execution */
            if (attgenerated == ATTRIBUTE_GENERATED_STORED)
            {
                ri_GeneratedExprs[i] = ExecPrepareExpr(expr, estate);
                ri_NumGeneratedNeeded++;
            }
 
            /* If UPDATE, mark column in resultRelInfo->ri_extraUpdatedCols */
            if (cmdtype == CMD_UPDATE)
                resultRelInfo->ri_extraUpdatedCols =
                    bms_add_member(resultRelInfo->ri_extraUpdatedCols,
                                   i + 1 - FirstLowInvalidHeapAttributeNumber);
        }
    }
 
    if (ri_NumGeneratedNeeded == 0)
    {
        /* didn't need it after all */
        pfree(ri_GeneratedExprs);
        ri_GeneratedExprs = NULL;
    }
 
    /* Save in appropriate set of fields */
    if (cmdtype == CMD_UPDATE)
    {
        /* Don't call twice */
        Assert(resultRelInfo->ri_GeneratedExprsU == NULL);
 
        resultRelInfo->ri_GeneratedExprsU = ri_GeneratedExprs;
        resultRelInfo->ri_NumGeneratedNeededU = ri_NumGeneratedNeeded;
 
        resultRelInfo->ri_extraUpdatedCols_valid = true;
    }
    else
    {
        /* Don't call twice */
        Assert(resultRelInfo->ri_GeneratedExprsI == NULL);
 
        resultRelInfo->ri_GeneratedExprsI = ri_GeneratedExprs;
        resultRelInfo->ri_NumGeneratedNeededI = ri_NumGeneratedNeeded;
    }
 
    MemoryContextSwitchTo(oldContext);
}
 
/*
 * Compute stored generated columns for a tuple
 */
void
ExecComputeStoredGenerated(ResultRelInfo *resultRelInfo,
                           EState *estate, TupleTableSlot *slot,
                           CmdType cmdtype)
{
    Relation    rel = resultRelInfo->ri_RelationDesc;
    TupleDesc   tupdesc = RelationGetDescr(rel);
    int         natts = tupdesc->natts;
    ExprContext *econtext = GetPerTupleExprContext(estate);
    ExprState **ri_GeneratedExprs;
    MemoryContext oldContext;
    Datum      *values;
    bool       *nulls;
 
    /* We should not be called unless this is true */
    Assert(tupdesc->constr && tupdesc->constr->has_generated_stored);
 
    /*
     * Initialize the expressions if we didn't already, and check whether we
     * can exit early because nothing needs to be computed.
     */
    if (cmdtype == CMD_UPDATE)
    {
        if (resultRelInfo->ri_GeneratedExprsU == NULL)
            ExecInitGenerated(resultRelInfo, estate, cmdtype);
        if (resultRelInfo->ri_NumGeneratedNeededU == 0)
            return;
        ri_GeneratedExprs = resultRelInfo->ri_GeneratedExprsU;
    }
    else
    {
        if (resultRelInfo->ri_GeneratedExprsI == NULL)
            ExecInitGenerated(resultRelInfo, estate, cmdtype);
        /* Early exit is impossible given the prior Assert */
        Assert(resultRelInfo->ri_NumGeneratedNeededI > 0);
        ri_GeneratedExprs = resultRelInfo->ri_GeneratedExprsI;
    }
 
    oldContext = MemoryContextSwitchTo(GetPerTupleMemoryContext(estate));
 
    values = palloc_array(Datum, natts);
    nulls = palloc_array(bool, natts);
 
    slot_getallattrs(slot);
    memcpy(nulls, slot->tts_isnull, sizeof(*nulls) * natts);
 
    for (int i = 0; i < natts; i++)
    {
        CompactAttribute *attr = TupleDescCompactAttr(tupdesc, i);
 
        if (ri_GeneratedExprs[i])
        {
            Datum       val;
            bool        isnull;
 
            Assert(TupleDescAttr(tupdesc, i)->attgenerated == ATTRIBUTE_GENERATED_STORED);
 
            econtext->ecxt_scantuple = slot;
 
            val = ExecEvalExpr(ri_GeneratedExprs[i], econtext, &isnull);
 
            /*
             * We must make a copy of val as we have no guarantees about where
             * memory for a pass-by-reference Datum is located.
             */
            if (!isnull)
                val = datumCopy(val, attr->attbyval, attr->attlen);
 
            values[i] = val;
            nulls[i] = isnull;
        }
        else
        {
            if (!nulls[i])
                values[i] = datumCopy(slot->tts_values[i], attr->attbyval, attr->attlen);
        }
    }
 
    ExecClearTuple(slot);
    memcpy(slot->tts_values, values, sizeof(*values) * natts);
    memcpy(slot->tts_isnull, nulls, sizeof(*nulls) * natts);
    ExecStoreVirtualTuple(slot);
    ExecMaterializeSlot(slot);
 
    MemoryContextSwitchTo(oldContext);
}
 
/*
 * ExecInitInsertProjection
 *      Do one-time initialization of projection data for INSERT tuples.
 *
 * INSERT queries may need a projection to filter out junk attrs in the tlist.
 *
 * This is also a convenient place to verify that the
 * output of an INSERT matches the target table.
 */
static void
ExecInitInsertProjection(ModifyTableState *mtstate,
                         ResultRelInfo *resultRelInfo)
{
    ModifyTable *node = (ModifyTable *) mtstate->ps.plan;
    Plan       *subplan = outerPlan(node);
    EState     *estate = mtstate->ps.state;
    List       *insertTargetList = NIL;
    bool        need_projection = false;
    ListCell   *l;
 
    /* Extract non-junk columns of the subplan's result tlist. */
    foreach(l, subplan->targetlist)
    {
        TargetEntry *tle = (TargetEntry *) lfirst(l);
 
        if (!tle->resjunk)
            insertTargetList = lappend(insertTargetList, tle);
        else
            need_projection = true;
    }
 
    /*
     * The junk-free list must produce a tuple suitable for the result
     * relation.
     */
    ExecCheckPlanOutput(resultRelInfo->ri_RelationDesc, insertTargetList);
 
    /* We'll need a slot matching the table's format. */
    resultRelInfo->ri_newTupleSlot =
        table_slot_create(resultRelInfo->ri_RelationDesc,
                          &estate->es_tupleTable);
 
    /* Build ProjectionInfo if needed (it probably isn't). */
    if (need_projection)
    {
        TupleDesc   relDesc = RelationGetDescr(resultRelInfo->ri_RelationDesc);
 
        /* need an expression context to do the projection */
        if (mtstate->ps.ps_ExprContext == NULL)
            ExecAssignExprContext(estate, &mtstate->ps);
 
        resultRelInfo->ri_projectNew =
            ExecBuildProjectionInfo(insertTargetList,
                                    mtstate->ps.ps_ExprContext,
                                    resultRelInfo->ri_newTupleSlot,
                                    &mtstate->ps,
                                    relDesc);
    }
 
    resultRelInfo->ri_projectNewInfoValid = true;
}
 
/*
 * ExecInitUpdateProjection
 *      Do one-time initialization of projection data for UPDATE tuples.
 *
 * UPDATE always needs a projection, because (1) there's always some junk
 * attrs, and (2) we may need to merge values of not-updated columns from
 * the old tuple into the final tuple.  In UPDATE, the tuple arriving from
 * the subplan contains only new values for the changed columns, plus row
 * identity info in the junk attrs.
 *
 * This is "one-time" for any given result rel, but we might touch more than
 * one result rel in the course of an inherited UPDATE, and each one needs
 * its own projection due to possible column order variation.
 *
 * This is also a convenient place to verify that the output of an UPDATE
 * matches the target table (ExecBuildUpdateProjection does that).
 */
static void
ExecInitUpdateProjection(ModifyTableState *mtstate,
                         ResultRelInfo *resultRelInfo)
{
    ModifyTable *node = (ModifyTable *) mtstate->ps.plan;
    Plan       *subplan = outerPlan(node);
    EState     *estate = mtstate->ps.state;
    TupleDesc   relDesc = RelationGetDescr(resultRelInfo->ri_RelationDesc);
    int         whichrel;
    List       *updateColnos;
 
    /*
     * Usually, mt_lastResultIndex matches the target rel.  If it happens not
     * to, we can get the index the hard way with an integer division.
     */
    whichrel = mtstate->mt_lastResultIndex;
    if (resultRelInfo != mtstate->resultRelInfo + whichrel)
    {
        whichrel = resultRelInfo - mtstate->resultRelInfo;
        Assert(whichrel >= 0 && whichrel < mtstate->mt_nrels);
    }
 
    updateColnos = (List *) list_nth(mtstate->mt_updateColnosLists, whichrel);
 
    /*
     * For UPDATE, we use the old tuple to fill up missing values in the tuple
     * produced by the subplan to get the new tuple.  We need two slots, both
     * matching the table's desired format.
     */
    resultRelInfo->ri_oldTupleSlot =
        table_slot_create(resultRelInfo->ri_RelationDesc,
                          &estate->es_tupleTable);
    resultRelInfo->ri_newTupleSlot =
        table_slot_create(resultRelInfo->ri_RelationDesc,
                          &estate->es_tupleTable);
 
    /* need an expression context to do the projection */
    if (mtstate->ps.ps_ExprContext == NULL)
        ExecAssignExprContext(estate, &mtstate->ps);
 
    resultRelInfo->ri_projectNew =
        ExecBuildUpdateProjection(subplan->targetlist,
                                  false,    /* subplan did the evaluation */
                                  updateColnos,
                                  relDesc,
                                  mtstate->ps.ps_ExprContext,
                                  resultRelInfo->ri_newTupleSlot,
                                  &mtstate->ps);
 
    resultRelInfo->ri_projectNewInfoValid = true;
}
 
/*
 * ExecGetInsertNewTuple
 *      This prepares a "new" tuple ready to be inserted into given result
 *      relation, by removing any junk columns of the plan's output tuple
 *      and (if necessary) coercing the tuple to the right tuple format.
 */
static TupleTableSlot *
ExecGetInsertNewTuple(ResultRelInfo *relinfo,
                      TupleTableSlot *planSlot)
{
    ProjectionInfo *newProj = relinfo->ri_projectNew;
    ExprContext *econtext;
 
    /*
     * If there's no projection to be done, just make sure the slot is of the
     * right type for the target rel.  If the planSlot is the right type we
     * can use it as-is, else copy the data into ri_newTupleSlot.
     */
    if (newProj == NULL)
    {
        if (relinfo->ri_newTupleSlot->tts_ops != planSlot->tts_ops)
        {
            ExecCopySlot(relinfo->ri_newTupleSlot, planSlot);
            return relinfo->ri_newTupleSlot;
        }
        else
            return planSlot;
    }
 
    /*
     * Else project; since the projection output slot is ri_newTupleSlot, this
     * will also fix any slot-type problem.
     *
     * Note: currently, this is dead code, because INSERT cases don't receive
     * any junk columns so there's never a projection to be done.
     */
    econtext = newProj->pi_exprContext;
    econtext->ecxt_outertuple = planSlot;
    return ExecProject(newProj);
}
 
/*
 * ExecGetUpdateNewTuple
 *      This prepares a "new" tuple by combining an UPDATE subplan's output
 *      tuple (which contains values of changed columns) with unchanged
 *      columns taken from the old tuple.
 *
 * The subplan tuple might also contain junk columns, which are ignored.
 * Note that the projection also ensures we have a slot of the right type.
 */
TupleTableSlot *
ExecGetUpdateNewTuple(ResultRelInfo *relinfo,
                      TupleTableSlot *planSlot,
                      TupleTableSlot *oldSlot)
{
    ProjectionInfo *newProj = relinfo->ri_projectNew;
    ExprContext *econtext;
 
    /* Use a few extra Asserts to protect against outside callers */
    Assert(relinfo->ri_projectNewInfoValid);
    Assert(planSlot != NULL && !TTS_EMPTY(planSlot));
    Assert(oldSlot != NULL && !TTS_EMPTY(oldSlot));
 
    econtext = newProj->pi_exprContext;
    econtext->ecxt_outertuple = planSlot;
    econtext->ecxt_scantuple = oldSlot;
    return ExecProject(newProj);
}
 
/* ----------------------------------------------------------------
 *      ExecInsert
 *
 *      For INSERT, we have to insert the tuple into the target relation
 *      (or partition thereof) and insert appropriate tuples into the index
 *      relations.
 *
 *      slot contains the new tuple value to be stored.
 *
 *      Returns RETURNING result if any, otherwise NULL.
 *      *inserted_tuple is the tuple that's effectively inserted;
 *      *insert_destrel is the relation where it was inserted.
 *      These are only set on success.
 *
 *      This may change the currently active tuple conversion map in
 *      mtstate->mt_transition_capture, so the callers must take care to
 *      save the previous value to avoid losing track of it.
 * ----------------------------------------------------------------
 */
static TupleTableSlot *
ExecInsert(ModifyTableContext *context,
           ResultRelInfo *resultRelInfo,
           TupleTableSlot *slot,
           bool canSetTag,
           TupleTableSlot **inserted_tuple,
           ResultRelInfo **insert_destrel)
{
    ModifyTableState *mtstate = context->mtstate;
    EState     *estate = context->estate;
    Relation    resultRelationDesc;
    List       *recheckIndexes = NIL;
    TupleTableSlot *planSlot = context->planSlot;
    TupleTableSlot *result = NULL;
    TransitionCaptureState *ar_insert_trig_tcs;
    ModifyTable *node = (ModifyTable *) mtstate->ps.plan;
    OnConflictAction onconflict = node->onConflictAction;
    PartitionTupleRouting *proute = mtstate->mt_partition_tuple_routing;
    MemoryContext oldContext;
 
    /*
     * If the input result relation is a partitioned table, find the leaf
     * partition to insert the tuple into.
     */
    if (proute)
    {
        ResultRelInfo *partRelInfo;
 
        slot = ExecPrepareTupleRouting(mtstate, estate, proute,
                                       resultRelInfo, slot,
                                       &partRelInfo);
        resultRelInfo = partRelInfo;
    }
 
    ExecMaterializeSlot(slot);
 
    resultRelationDesc = resultRelInfo->ri_RelationDesc;
 
    /*
     * Open the table's indexes, if we have not done so already, so that we
     * can add new index entries for the inserted tuple.
     */
    if (resultRelationDesc->rd_rel->relhasindex &&
        resultRelInfo->ri_IndexRelationDescs == NULL)
        ExecOpenIndices(resultRelInfo, onconflict != ONCONFLICT_NONE);
 
    /*
     * BEFORE ROW INSERT Triggers.
     *
     * Note: We fire BEFORE ROW TRIGGERS for every attempted insertion in an
     * INSERT ... ON CONFLICT statement.  We cannot check for constraint
     * violations before firing these triggers, because they can change the
     * values to insert.  Also, they can run arbitrary user-defined code with
     * side-effects that we can't cancel by just not inserting the tuple.
     */
    if (resultRelInfo->ri_TrigDesc &&
        resultRelInfo->ri_TrigDesc->trig_insert_before_row)
    {
        /* Flush any pending inserts, so rows are visible to the triggers */
        if (estate->es_insert_pending_result_relations != NIL)
            ExecPendingInserts(estate);
 
        if (!ExecBRInsertTriggers(estate, resultRelInfo, slot))
            return NULL;        /* "do nothing" */
    }
 
    /* INSTEAD OF ROW INSERT Triggers */
    if (resultRelInfo->ri_TrigDesc &&
        resultRelInfo->ri_TrigDesc->trig_insert_instead_row)
    {
        if (!ExecIRInsertTriggers(estate, resultRelInfo, slot))
            return NULL;        /* "do nothing" */
    }
    else if (resultRelInfo->ri_FdwRoutine)
    {
        /*
         * GENERATED expressions might reference the tableoid column, so
         * (re-)initialize tts_tableOid before evaluating them.
         */
        slot->tts_tableOid = RelationGetRelid(resultRelInfo->ri_RelationDesc);
 
        /*
         * Compute stored generated columns
         */
        if (resultRelationDesc->rd_att->constr &&
            resultRelationDesc->rd_att->constr->has_generated_stored)
            ExecComputeStoredGenerated(resultRelInfo, estate, slot,
                                       CMD_INSERT);
 
        /*
         * If the FDW supports batching, and batching is requested, accumulate
         * rows and insert them in batches. Otherwise use the per-row inserts.
         */
        if (resultRelInfo->ri_BatchSize > 1)
        {
            bool        flushed = false;
 
            /*
             * When we've reached the desired batch size, perform the
             * insertion.
             */
            if (resultRelInfo->ri_NumSlots == resultRelInfo->ri_BatchSize)
            {
                ExecBatchInsert(mtstate, resultRelInfo,
                                resultRelInfo->ri_Slots,
                                resultRelInfo->ri_PlanSlots,
                                resultRelInfo->ri_NumSlots,
                                estate, canSetTag);
                flushed = true;
            }
 
            oldContext = MemoryContextSwitchTo(estate->es_query_cxt);
 
            if (resultRelInfo->ri_Slots == NULL)
            {
                resultRelInfo->ri_Slots = palloc_array(TupleTableSlot *, resultRelInfo->ri_BatchSize);
                resultRelInfo->ri_PlanSlots = palloc_array(TupleTableSlot *, resultRelInfo->ri_BatchSize);
            }
 
            /*
             * Initialize the batch slots. We don't know how many slots will
             * be needed, so we initialize them as the batch grows, and we
             * keep them across batches. To mitigate an inefficiency in how
             * resource owner handles objects with many references (as with
             * many slots all referencing the same tuple descriptor) we copy
             * the appropriate tuple descriptor for each slot.
             */
            if (resultRelInfo->ri_NumSlots >= resultRelInfo->ri_NumSlotsInitialized)
            {
                TupleDesc   tdesc = CreateTupleDescCopy(slot->tts_tupleDescriptor);
                TupleDesc   plan_tdesc =
                    CreateTupleDescCopy(planSlot->tts_tupleDescriptor);
 
                resultRelInfo->ri_Slots[resultRelInfo->ri_NumSlots] =
                    MakeSingleTupleTableSlot(tdesc, slot->tts_ops);
 
                resultRelInfo->ri_PlanSlots[resultRelInfo->ri_NumSlots] =
                    MakeSingleTupleTableSlot(plan_tdesc, planSlot->tts_ops);
 
                /* remember how many batch slots we initialized */
                resultRelInfo->ri_NumSlotsInitialized++;
            }
 
            ExecCopySlot(resultRelInfo->ri_Slots[resultRelInfo->ri_NumSlots],
                         slot);
 
            ExecCopySlot(resultRelInfo->ri_PlanSlots[resultRelInfo->ri_NumSlots],
                         planSlot);
 
            /*
             * If these are the first tuples stored in the buffers, add the
             * target rel and the mtstate to the
             * es_insert_pending_result_relations and
             * es_insert_pending_modifytables lists respectively, except in
             * the case where flushing was done above, in which case they
             * would already have been added to the lists, so no need to do
             * this.
             */
            if (resultRelInfo->ri_NumSlots == 0 && !flushed)
            {
                Assert(!list_member_ptr(estate->es_insert_pending_result_relations,
                                        resultRelInfo));
                estate->es_insert_pending_result_relations =
                    lappend(estate->es_insert_pending_result_relations,
                            resultRelInfo);
                estate->es_insert_pending_modifytables =
                    lappend(estate->es_insert_pending_modifytables, mtstate);
            }
            Assert(list_member_ptr(estate->es_insert_pending_result_relations,
                                   resultRelInfo));
 
            resultRelInfo->ri_NumSlots++;
 
            MemoryContextSwitchTo(oldContext);
 
            return NULL;
        }
 
        /*
         * insert into foreign table: let the FDW do it
         */
        slot = resultRelInfo->ri_FdwRoutine->ExecForeignInsert(estate,
                                                               resultRelInfo,
                                                               slot,
                                                               planSlot);
 
        if (slot == NULL)       /* "do nothing" */
            return NULL;
 
        /*
         * AFTER ROW Triggers or RETURNING expressions might reference the
         * tableoid column, so (re-)initialize tts_tableOid before evaluating
         * them.  (This covers the case where the FDW replaced the slot.)
         */
        slot->tts_tableOid = RelationGetRelid(resultRelInfo->ri_RelationDesc);
    }
    else
    {
        WCOKind     wco_kind;
 
        /*
         * Constraints and GENERATED expressions might reference the tableoid
         * column, so (re-)initialize tts_tableOid before evaluating them.
         */
        slot->tts_tableOid = RelationGetRelid(resultRelationDesc);
 
        /*
         * Compute stored generated columns
         */
        if (resultRelationDesc->rd_att->constr &&
            resultRelationDesc->rd_att->constr->has_generated_stored)
            ExecComputeStoredGenerated(resultRelInfo, estate, slot,
                                       CMD_INSERT);
 
        /*
         * Check any RLS WITH CHECK policies.
         *
         * Normally we should check INSERT policies. But if the insert is the
         * result of a partition key update that moved the tuple to a new
         * partition, we should instead check UPDATE policies, because we are
         * executing policies defined on the target table, and not those
         * defined on the child partitions.
         *
         * If we're running MERGE, we refer to the action that we're executing
         * to know if we're doing an INSERT or UPDATE to a partition table.
         */
        if (mtstate->operation == CMD_UPDATE)
            wco_kind = WCO_RLS_UPDATE_CHECK;
        else if (mtstate->operation == CMD_MERGE)
            wco_kind = (mtstate->mt_merge_action->mas_action->commandType == CMD_UPDATE) ?
                WCO_RLS_UPDATE_CHECK : WCO_RLS_INSERT_CHECK;
        else
            wco_kind = WCO_RLS_INSERT_CHECK;
 
        /*
         * ExecWithCheckOptions() will skip any WCOs which are not of the kind
         * we are looking for at this point.
         */
        if (resultRelInfo->ri_WithCheckOptions != NIL)
            ExecWithCheckOptions(wco_kind, resultRelInfo, slot, estate);
 
        /*
         * Check the constraints of the tuple.
         */
        if (resultRelationDesc->rd_att->constr)
            ExecConstraints(resultRelInfo, slot, estate);
 
        /*
         * Also check the tuple against the partition constraint, if there is
         * one; except that if we got here via tuple-routing, we don't need to
         * if there's no BR trigger defined on the partition.
         */
        if (resultRelationDesc->rd_rel->relispartition &&
            (resultRelInfo->ri_RootResultRelInfo == NULL ||
             (resultRelInfo->ri_TrigDesc &&
              resultRelInfo->ri_TrigDesc->trig_insert_before_row)))
            ExecPartitionCheck(resultRelInfo, slot, estate, true);
 
        if (onconflict != ONCONFLICT_NONE && resultRelInfo->ri_NumIndices > 0)
        {
            /* Perform a speculative insertion. */
            uint32      specToken;
            ItemPointerData conflictTid;
            ItemPointerData invalidItemPtr;
            bool        specConflict;
            List       *arbiterIndexes;
 
            ItemPointerSetInvalid(&invalidItemPtr);
            arbiterIndexes = resultRelInfo->ri_onConflictArbiterIndexes;
 
            /*
             * Do a non-conclusive check for conflicts first.
             *
             * We're not holding any locks yet, so this doesn't guarantee that
             * the later insert won't conflict.  But it avoids leaving behind
             * a lot of canceled speculative insertions, if you run a lot of
             * INSERT ON CONFLICT statements that do conflict.
             *
             * We loop back here if we find a conflict below, either during
             * the pre-check, or when we re-check after inserting the tuple
             * speculatively.  Better allow interrupts in case some bug makes
             * this an infinite loop.
             */
    vlock:
            CHECK_FOR_INTERRUPTS();
            specConflict = false;
            if (!ExecCheckIndexConstraints(resultRelInfo, slot, estate,
                                           &conflictTid, &invalidItemPtr,
                                           arbiterIndexes))
            {
                /* committed conflict tuple found */
                if (onconflict == ONCONFLICT_UPDATE)
                {
                    /*
                     * In case of ON CONFLICT DO UPDATE, execute the UPDATE
                     * part.  Be prepared to retry if the UPDATE fails because
                     * of another concurrent UPDATE/DELETE to the conflict
                     * tuple.
                     */
                    TupleTableSlot *returning = NULL;
 
                    if (ExecOnConflictUpdate(context, resultRelInfo,
                                             &conflictTid, slot, canSetTag,
                                             &returning))
                    {
                        InstrCountTuples2(&mtstate->ps, 1);
                        return returning;
                    }
                    else
                        goto vlock;
                }
                else if (onconflict == ONCONFLICT_SELECT)
                {
                    /*
                     * In case of ON CONFLICT DO SELECT, optionally lock the
                     * conflicting tuple, fetch it and project RETURNING on
                     * it. Be prepared to retry if locking fails because of a
                     * concurrent UPDATE/DELETE to the conflict tuple.
                     */
                    TupleTableSlot *returning = NULL;
 
                    if (ExecOnConflictSelect(context, resultRelInfo,
                                             &conflictTid, slot, canSetTag,
                                             &returning))
                    {
                        InstrCountTuples2(&mtstate->ps, 1);
                        return returning;
                    }
                    else
                        goto vlock;
                }
                else
                {
                    /*
                     * In case of ON CONFLICT DO NOTHING, do nothing. However,
                     * verify that the tuple is visible to the executor's MVCC
                     * snapshot at higher isolation levels.
                     *
                     * Using ExecGetReturningSlot() to store the tuple for the
                     * recheck isn't that pretty, but we can't trivially use
                     * the input slot, because it might not be of a compatible
                     * type. As there's no conflicting usage of
                     * ExecGetReturningSlot() in the DO NOTHING case...
                     */
                    Assert(onconflict == ONCONFLICT_NOTHING);
                    ExecCheckTIDVisible(estate, resultRelInfo, &conflictTid,
                                        ExecGetReturningSlot(estate, resultRelInfo));
                    InstrCountTuples2(&mtstate->ps, 1);
                    return NULL;
                }
            }
 
            /*
             * Before we start insertion proper, acquire our "speculative
             * insertion lock".  Others can use that to wait for us to decide
             * if we're going to go ahead with the insertion, instead of
             * waiting for the whole transaction to complete.
             */
            INJECTION_POINT("exec-insert-before-insert-speculative", NULL);
            specToken = SpeculativeInsertionLockAcquire(GetCurrentTransactionId());
 
            /* insert the tuple, with the speculative token */
            table_tuple_insert_speculative(resultRelationDesc, slot,
                                           estate->es_output_cid,
                                           0,
                                           NULL,
                                           specToken);
 
            /* insert index entries for tuple */
            recheckIndexes = ExecInsertIndexTuples(resultRelInfo,
                                                   estate, EIIT_NO_DUPE_ERROR,
                                                   slot, arbiterIndexes,
                                                   &specConflict);
 
            /* adjust the tuple's state accordingly */
            table_tuple_complete_speculative(resultRelationDesc, slot,
                                             specToken, !specConflict);
 
            /*
             * Wake up anyone waiting for our decision.  They will re-check
             * the tuple, see that it's no longer speculative, and wait on our
             * XID as if this was a regularly inserted tuple all along.  Or if
             * we killed the tuple, they will see it's dead, and proceed as if
             * the tuple never existed.
             */
            SpeculativeInsertionLockRelease(GetCurrentTransactionId());
 
            /*
             * If there was a conflict, start from the beginning.  We'll do
             * the pre-check again, which will now find the conflicting tuple
             * (unless it aborts before we get there).
             */
            if (specConflict)
            {
                list_free(recheckIndexes);
                goto vlock;
            }
 
            /* Since there was no insertion conflict, we're done */
        }
        else
        {
            /* insert the tuple normally */
            table_tuple_insert(resultRelationDesc, slot,
                               estate->es_output_cid,
                               0, NULL);
 
            /* insert index entries for tuple */
            if (resultRelInfo->ri_NumIndices > 0)
                recheckIndexes = ExecInsertIndexTuples(resultRelInfo, estate,
                                                       0, slot, NIL,
                                                       NULL);
        }
    }
 
    if (canSetTag)
        (estate->es_processed)++;
 
    /*
     * If this insert is the result of a partition key update that moved the
     * tuple to a new partition, put this row into the transition NEW TABLE,
     * if there is one. We need to do this separately for DELETE and INSERT
     * because they happen on different tables.
     */
    ar_insert_trig_tcs = mtstate->mt_transition_capture;
    if (mtstate->operation == CMD_UPDATE && mtstate->mt_transition_capture
        && mtstate->mt_transition_capture->tcs_update_new_table)
    {
        ExecARUpdateTriggers(estate, resultRelInfo,
                             NULL, NULL,
                             NULL,
                             NULL,
                             slot,
                             NULL,
                             mtstate->mt_transition_capture,
                             false);
 
        /*
         * We've already captured the NEW TABLE row, so make sure any AR
         * INSERT trigger fired below doesn't capture it again.
         */
        ar_insert_trig_tcs = NULL;
    }
 
    /* AFTER ROW INSERT Triggers */
    ExecARInsertTriggers(estate, resultRelInfo, slot, recheckIndexes,
                         ar_insert_trig_tcs);
 
    list_free(recheckIndexes);
 
    /*
     * Check any WITH CHECK OPTION constraints from parent views.  We are
     * required to do this after testing all constraints and uniqueness
     * violations per the SQL spec, so we do it after actually inserting the
     * record into the heap and all indexes.
     *
     * ExecWithCheckOptions will elog(ERROR) if a violation is found, so the
     * tuple will never be seen, if it violates the WITH CHECK OPTION.
     *
     * ExecWithCheckOptions() will skip any WCOs which are not of the kind we
     * are looking for at this point.
     */
    if (resultRelInfo->ri_WithCheckOptions != NIL)
        ExecWithCheckOptions(WCO_VIEW_CHECK, resultRelInfo, slot, estate);
 
    /* Process RETURNING if present */
    if (resultRelInfo->ri_projectReturning)
    {
        TupleTableSlot *oldSlot = NULL;
 
        /*
         * If this is part of a cross-partition UPDATE, and the RETURNING list
         * refers to any OLD columns, ExecDelete() will have saved the tuple
         * deleted from the original partition, which we must use here to
         * compute the OLD column values.  Otherwise, all OLD column values
         * will be NULL.
         */
        if (context->cpDeletedSlot)
        {
            TupleConversionMap *tupconv_map;
 
            /*
             * Convert the OLD tuple to the new partition's format/slot, if
             * needed.  Note that ExecDelete() already converted it to the
             * root's partition's format/slot.
             */
            oldSlot = context->cpDeletedSlot;
            tupconv_map = ExecGetRootToChildMap(resultRelInfo, estate);
            if (tupconv_map != NULL)
            {
                oldSlot = execute_attr_map_slot(tupconv_map->attrMap,
                                                oldSlot,
                                                ExecGetReturningSlot(estate,
                                                                     resultRelInfo));
 
                oldSlot->tts_tableOid = context->cpDeletedSlot->tts_tableOid;
                ItemPointerCopy(&context->cpDeletedSlot->tts_tid, &oldSlot->tts_tid);
            }
        }
 
        result = ExecProcessReturning(context, resultRelInfo, false,
                                      oldSlot, slot, planSlot);
 
        /*
         * For a cross-partition UPDATE, release the old tuple, first making
         * sure that the result slot has a local copy of any pass-by-reference
         * values.
         */
        if (context->cpDeletedSlot)
        {
            ExecMaterializeSlot(result);
            ExecClearTuple(oldSlot);
            if (context->cpDeletedSlot != oldSlot)
                ExecClearTuple(context->cpDeletedSlot);
            context->cpDeletedSlot = NULL;
        }
    }
 
    if (inserted_tuple)
        *inserted_tuple = slot;
    if (insert_destrel)
        *insert_destrel = resultRelInfo;
 
    return result;
}
 
/* ----------------------------------------------------------------
 *      ExecForPortionOfLeftovers
 *
 *      Insert tuples for the untouched portion of a row in a FOR
 *      PORTION OF UPDATE/DELETE
 * ----------------------------------------------------------------
 */
static void
ExecForPortionOfLeftovers(ModifyTableContext *context,
                          EState *estate,
                          ResultRelInfo *resultRelInfo,
                          ItemPointer tupleid)
{
    ModifyTableState *mtstate = context->mtstate;
    ModifyTable *node = (ModifyTable *) mtstate->ps.plan;
    ForPortionOfExpr *forPortionOf = (ForPortionOfExpr *) node->forPortionOf;
    AttrNumber  rangeAttno;
    Datum       oldRange;
    TypeCacheEntry *typcache;
    ForPortionOfState *fpoState;
    TupleTableSlot *oldtupleSlot;
    TupleTableSlot *leftoverSlot;
    TupleConversionMap *map = NULL;
    HeapTuple   oldtuple = NULL;
    CmdType     oldOperation;
    TransitionCaptureState *oldTcs;
    FmgrInfo    flinfo;
    PgStat_FunctionCallUsage fcusage;
    ReturnSetInfo rsi;
    bool        didInit = false;
    bool        shouldFree = false;
 
    LOCAL_FCINFO(fcinfo, 2);
 
    if (!resultRelInfo->ri_forPortionOf)
    {
        /*
         * If we don't have a ForPortionOfState yet, we must be a partition
         * child being hit for the first time. Make a copy from the root, with
         * our own TupleTableSlot. We do this lazily so that we don't pay the
         * price of unused partitions.
         */
        ForPortionOfState *leafState = makeNode(ForPortionOfState);
 
        if (!mtstate->rootResultRelInfo)
            elog(ERROR, "no root relation but ri_forPortionOf is uninitialized");
 
        fpoState = mtstate->rootResultRelInfo->ri_forPortionOf;
        Assert(fpoState);
 
        leafState->fp_rangeName = fpoState->fp_rangeName;
        leafState->fp_rangeType = fpoState->fp_rangeType;
        leafState->fp_rangeAttno = fpoState->fp_rangeAttno;
        leafState->fp_targetRange = fpoState->fp_targetRange;
        leafState->fp_Leftover = fpoState->fp_Leftover;
        /* Each partition needs a slot matching its tuple descriptor */
        leafState->fp_Existing =
            table_slot_create(resultRelInfo->ri_RelationDesc,
                              &mtstate->ps.state->es_tupleTable);
 
        resultRelInfo->ri_forPortionOf = leafState;
    }
    fpoState = resultRelInfo->ri_forPortionOf;
    oldtupleSlot = fpoState->fp_Existing;
    leftoverSlot = fpoState->fp_Leftover;
 
    /*
     * Get the old pre-UPDATE/DELETE tuple. We will use its range to compute
     * untouched parts of history, and if necessary we will insert copies with
     * truncated start/end times.
     *
     * We have already locked the tuple in ExecUpdate/ExecDelete, and it has
     * passed EvalPlanQual. This ensures that concurrent updates in READ
     * COMMITTED can't insert conflicting temporal leftovers.
     *
     * It does *not* protect against concurrent update/deletes overlooking
     * each others' leftovers though. See our isolation tests for details
     * about that and a viable workaround.
     */
    if (!table_tuple_fetch_row_version(resultRelInfo->ri_RelationDesc, tupleid, SnapshotAny, oldtupleSlot))
        elog(ERROR, "failed to fetch tuple for FOR PORTION OF");
 
    /*
     * Get the old range of the record being updated/deleted. Must read with
     * the attno of the leaf partition being updated.
     */
 
    rangeAttno = forPortionOf->rangeVar->varattno;
    if (resultRelInfo->ri_RootResultRelInfo)
        map = ExecGetChildToRootMap(resultRelInfo);
    if (map != NULL)
        rangeAttno = map->attrMap->attnums[rangeAttno - 1];
    slot_getallattrs(oldtupleSlot);
 
    if (oldtupleSlot->tts_isnull[rangeAttno - 1])
        elog(ERROR, "found a NULL range in a temporal table");
    oldRange = oldtupleSlot->tts_values[rangeAttno - 1];
 
    /*
     * Get the range's type cache entry. This is worth caching for the whole
     * UPDATE/DELETE as range functions do.
     */
 
    typcache = fpoState->fp_leftoverstypcache;
    if (typcache == NULL)
    {
        typcache = lookup_type_cache(forPortionOf->rangeType, 0);
        fpoState->fp_leftoverstypcache = typcache;
    }
 
    /*
     * Get the ranges to the left/right of the targeted range. We call a SETOF
     * support function and insert as many temporal leftovers as it gives us.
     * Although rangetypes have 0/1/2 leftovers, multiranges have 0/1, and
     * other types may have more.
     */
 
    fmgr_info(forPortionOf->withoutPortionProc, &flinfo);
    rsi.type = T_ReturnSetInfo;
    rsi.econtext = mtstate->ps.ps_ExprContext;
    rsi.expectedDesc = NULL;
    rsi.allowedModes = (int) (SFRM_ValuePerCall);
    rsi.returnMode = SFRM_ValuePerCall;
    /* isDone is filled below */
    rsi.setResult = NULL;
    rsi.setDesc = NULL;
 
    InitFunctionCallInfoData(*fcinfo, &flinfo, 2, InvalidOid, NULL, (Node *) &rsi);
    fcinfo->args[0].value = oldRange;
    fcinfo->args[0].isnull = false;
    fcinfo->args[1].value = fpoState->fp_targetRange;
    fcinfo->args[1].isnull = false;
 
    /*
     * If there are partitions, we must insert into the root table, so we get
     * tuple routing. We already set up leftoverSlot with the root tuple
     * descriptor.
     */
    if (resultRelInfo->ri_RootResultRelInfo)
        resultRelInfo = resultRelInfo->ri_RootResultRelInfo;
 
    /*
     * Insert a leftover for each value returned by the without_portion helper
     * function
     */
    while (true)
    {
        Datum       leftover;
 
        /* Call the function one time */
        pgstat_init_function_usage(fcinfo, &fcusage);
 
        fcinfo->isnull = false;
        rsi.isDone = ExprSingleResult;
        leftover = FunctionCallInvoke(fcinfo);
 
        pgstat_end_function_usage(&fcusage,
                                  rsi.isDone != ExprMultipleResult);
 
        if (rsi.returnMode != SFRM_ValuePerCall)
            elog(ERROR, "without_portion function violated function call protocol");
 
        /* Are we done? */
        if (rsi.isDone == ExprEndResult)
            break;
 
        if (fcinfo->isnull)
            elog(ERROR, "got a null from without_portion function");
 
        /*
         * Does the new Datum violate domain checks? Row-level CHECK
         * constraints are validated by ExecInsert, so we don't need to do
         * anything here for those.
         */
        if (forPortionOf->isDomain)
            domain_check(leftover, false, forPortionOf->rangeVar->vartype, NULL, NULL);
 
        if (!didInit)
        {
            /*
             * Make a copy of the pre-UPDATE row. Then we'll overwrite the
             * range column below. Convert oldtuple to the base table's format
             * if necessary. We need to insert temporal leftovers through the
             * root partition so they get routed correctly.
             */
            if (map != NULL)
            {
                leftoverSlot = execute_attr_map_slot(map->attrMap,
                                                     oldtupleSlot,
                                                     leftoverSlot);
            }
            else
            {
                oldtuple = ExecFetchSlotHeapTuple(oldtupleSlot, false, &shouldFree);
                ExecForceStoreHeapTuple(oldtuple, leftoverSlot, false);
            }
 
            /*
             * Save some mtstate things so we can restore them below. XXX:
             * Should we create our own ModifyTableState instead?
             */
            oldOperation = mtstate->operation;
            mtstate->operation = CMD_INSERT;
            oldTcs = mtstate->mt_transition_capture;
 
            didInit = true;
        }
 
        leftoverSlot->tts_values[forPortionOf->rangeVar->varattno - 1] = leftover;
        leftoverSlot->tts_isnull[forPortionOf->rangeVar->varattno - 1] = false;
        ExecMaterializeSlot(leftoverSlot);
 
        /*
         * The standard says that each temporal leftover should execute its
         * own INSERT statement, firing all statement and row triggers, but
         * skipping insert permission checks. Therefore we give each insert
         * its own transition table. If we just push & pop a new trigger level
         * for each insert, we get exactly what we need.
         *
         * We have to make sure that the inserts don't add to the ROW_COUNT
         * diagnostic or the command tag, so we pass false for canSetTag.
         */
        AfterTriggerBeginQuery();
        ExecSetupTransitionCaptureState(mtstate, estate);
        fireBSTriggers(mtstate);
        ExecInsert(context, resultRelInfo, leftoverSlot, false, NULL, NULL);
        fireASTriggers(mtstate);
        AfterTriggerEndQuery(estate);
    }
 
    if (didInit)
    {
        mtstate->operation = oldOperation;
        mtstate->mt_transition_capture = oldTcs;
 
        if (shouldFree)
            heap_freetuple(oldtuple);
    }
}
 
/* ----------------------------------------------------------------
 *      ExecBatchInsert
 *
 *      Insert multiple tuples in an efficient way.
 *      Currently, this handles inserting into a foreign table without
 *      RETURNING clause.
 * ----------------------------------------------------------------
 */
static void
ExecBatchInsert(ModifyTableState *mtstate,
                ResultRelInfo *resultRelInfo,
                TupleTableSlot **slots,
                TupleTableSlot **planSlots,
                int numSlots,
                EState *estate,
                bool canSetTag)
{
    int         i;
    int         numInserted = numSlots;
    TupleTableSlot *slot = NULL;
    TupleTableSlot **rslots;
 
    /*
     * insert into foreign table: let the FDW do it
     */
    rslots = resultRelInfo->ri_FdwRoutine->ExecForeignBatchInsert(estate,
                                                                  resultRelInfo,
                                                                  slots,
                                                                  planSlots,
                                                                  &numInserted);
 
    for (i = 0; i < numInserted; i++)
    {
        slot = rslots[i];
 
        /*
         * AFTER ROW Triggers might reference the tableoid column, so
         * (re-)initialize tts_tableOid before evaluating them.
         */
        slot->tts_tableOid = RelationGetRelid(resultRelInfo->ri_RelationDesc);
 
        /* AFTER ROW INSERT Triggers */
        ExecARInsertTriggers(estate, resultRelInfo, slot, NIL,
                             mtstate->mt_transition_capture);
 
        /*
         * Check any WITH CHECK OPTION constraints from parent views.  See the
         * comment in ExecInsert.
         */
        if (resultRelInfo->ri_WithCheckOptions != NIL)
            ExecWithCheckOptions(WCO_VIEW_CHECK, resultRelInfo, slot, estate);
    }
 
    if (canSetTag && numInserted > 0)
        estate->es_processed += numInserted;
 
    /* Clean up all the slots, ready for the next batch */
    for (i = 0; i < numSlots; i++)
    {
        ExecClearTuple(slots[i]);
        ExecClearTuple(planSlots[i]);
    }
    resultRelInfo->ri_NumSlots = 0;
}
 
/*
 * ExecPendingInserts -- flushes all pending inserts to the foreign tables
 */
static void
ExecPendingInserts(EState *estate)
{
    ListCell   *l1,
               *l2;
 
    forboth(l1, estate->es_insert_pending_result_relations,
            l2, estate->es_insert_pending_modifytables)
    {
        ResultRelInfo *resultRelInfo = (ResultRelInfo *) lfirst(l1);
        ModifyTableState *mtstate = (ModifyTableState *) lfirst(l2);
 
        Assert(mtstate);
        ExecBatchInsert(mtstate, resultRelInfo,
                        resultRelInfo->ri_Slots,
                        resultRelInfo->ri_PlanSlots,
                        resultRelInfo->ri_NumSlots,
                        estate, mtstate->canSetTag);
    }
 
    list_free(estate->es_insert_pending_result_relations);
    list_free(estate->es_insert_pending_modifytables);
    estate->es_insert_pending_result_relations = NIL;
    estate->es_insert_pending_modifytables = NIL;
}
 
/*
 * ExecDeletePrologue -- subroutine for ExecDelete
 *
 * Prepare executor state for DELETE.  Actually, the only thing we have to do
 * here is execute BEFORE ROW triggers.  We return false if one of them makes
 * the delete a no-op; otherwise, return true.
 */
static bool
ExecDeletePrologue(ModifyTableContext *context, ResultRelInfo *resultRelInfo,
                   ItemPointer tupleid, HeapTuple oldtuple,
                   TupleTableSlot **epqreturnslot, TM_Result *result)
{
    if (result)
        *result = TM_Ok;
 
    /* BEFORE ROW DELETE triggers */
    if (resultRelInfo->ri_TrigDesc &&
        resultRelInfo->ri_TrigDesc->trig_delete_before_row)
    {
        /* Flush any pending inserts, so rows are visible to the triggers */
        if (context->estate->es_insert_pending_result_relations != NIL)
            ExecPendingInserts(context->estate);
 
        return ExecBRDeleteTriggers(context->estate, context->epqstate,
                                    resultRelInfo, tupleid, oldtuple,
                                    epqreturnslot, result, &context->tmfd,
                                    context->mtstate->operation == CMD_MERGE);
    }
 
    return true;
}
 
/*
 * ExecDeleteAct -- subroutine for ExecDelete
 *
 * Actually delete the tuple from a plain table.
 *
 * Caller is in charge of doing EvalPlanQual as necessary
 */
static TM_Result
ExecDeleteAct(ModifyTableContext *context, ResultRelInfo *resultRelInfo,
              ItemPointer tupleid, bool changingPart)
{
    EState     *estate = context->estate;
    uint32      options = 0;
 
    if (changingPart)
        options |= TABLE_DELETE_CHANGING_PARTITION;
 
    return table_tuple_delete(resultRelInfo->ri_RelationDesc, tupleid,
                              estate->es_output_cid,
                              options,
                              estate->es_snapshot,
                              estate->es_crosscheck_snapshot,
                              true /* wait for commit */ ,
                              &context->tmfd);
}
 
/*
 * ExecDeleteEpilogue -- subroutine for ExecDelete
 *
 * Closing steps of tuple deletion; this invokes AFTER FOR EACH ROW triggers,
 * including the UPDATE triggers if the deletion is being done as part of a
 * cross-partition tuple move. It also inserts temporal leftovers from a
 * DELETE FOR PORTION OF.
 */
static void
ExecDeleteEpilogue(ModifyTableContext *context, ResultRelInfo *resultRelInfo,
                   ItemPointer tupleid, HeapTuple oldtuple, bool changingPart)
{
    ModifyTableState *mtstate = context->mtstate;
    EState     *estate = context->estate;
    TransitionCaptureState *ar_delete_trig_tcs;
 
    /*
     * If this delete is the result of a partition key update that moved the
     * tuple to a new partition, put this row into the transition OLD TABLE,
     * if there is one. We need to do this separately for DELETE and INSERT
     * because they happen on different tables.
     */
    ar_delete_trig_tcs = mtstate->mt_transition_capture;
    if (mtstate->operation == CMD_UPDATE && mtstate->mt_transition_capture &&
        mtstate->mt_transition_capture->tcs_update_old_table)
    {
        ExecARUpdateTriggers(estate, resultRelInfo,
                             NULL, NULL,
                             tupleid, oldtuple,
                             NULL, NULL, mtstate->mt_transition_capture,
                             false);
 
        /*
         * We've already captured the OLD TABLE row, so make sure any AR
         * DELETE trigger fired below doesn't capture it again.
         */
        ar_delete_trig_tcs = NULL;
    }
 
    /* Compute temporal leftovers in FOR PORTION OF */
    if (((ModifyTable *) context->mtstate->ps.plan)->forPortionOf)
        ExecForPortionOfLeftovers(context, estate, resultRelInfo, tupleid);
 
    /* AFTER ROW DELETE Triggers */
    ExecARDeleteTriggers(estate, resultRelInfo, tupleid, oldtuple,
                         ar_delete_trig_tcs, changingPart);
}
 
/* ----------------------------------------------------------------
 *      ExecDelete
 *
 *      DELETE is like UPDATE, except that we delete the tuple and no
 *      index modifications are needed.
 *
 *      When deleting from a table, tupleid identifies the tuple to delete and
 *      oldtuple is NULL.  When deleting through a view INSTEAD OF trigger,
 *      oldtuple is passed to the triggers and identifies what to delete, and
 *      tupleid is invalid.  When deleting from a foreign table, tupleid is
 *      invalid; the FDW has to figure out which row to delete using data from
 *      the planSlot.  oldtuple is passed to foreign table triggers; it is
 *      NULL when the foreign table has no relevant triggers.  We use
 *      tupleDeleted to indicate whether the tuple is actually deleted,
 *      callers can use it to decide whether to continue the operation.  When
 *      this DELETE is a part of an UPDATE of partition-key, then the slot
 *      returned by EvalPlanQual() is passed back using output parameter
 *      epqreturnslot.
 *
 *      Returns RETURNING result if any, otherwise NULL.
 * ----------------------------------------------------------------
 */
static TupleTableSlot *
ExecDelete(ModifyTableContext *context,
           ResultRelInfo *resultRelInfo,
           ItemPointer tupleid,
           HeapTuple oldtuple,
           bool processReturning,
           bool changingPart,
           bool canSetTag,
           TM_Result *tmresult,
           bool *tupleDeleted,
           TupleTableSlot **epqreturnslot)
{
    EState     *estate = context->estate;
    Relation    resultRelationDesc = resultRelInfo->ri_RelationDesc;
    TupleTableSlot *slot = NULL;
    TM_Result   result;
    bool        saveOld;
 
    if (tupleDeleted)
        *tupleDeleted = false;
 
    /*
     * Prepare for the delete.  This includes BEFORE ROW triggers, so we're
     * done if it says we are.
     */
    if (!ExecDeletePrologue(context, resultRelInfo, tupleid, oldtuple,
                            epqreturnslot, tmresult))
        return NULL;
 
    /* INSTEAD OF ROW DELETE Triggers */
    if (resultRelInfo->ri_TrigDesc &&
        resultRelInfo->ri_TrigDesc->trig_delete_instead_row)
    {
        bool        dodelete;
 
        Assert(oldtuple != NULL);
        dodelete = ExecIRDeleteTriggers(estate, resultRelInfo, oldtuple);
 
        if (!dodelete)          /* "do nothing" */
            return NULL;
    }
    else if (resultRelInfo->ri_FdwRoutine)
    {
        /*
         * delete from foreign table: let the FDW do it
         *
         * We offer the returning slot as a place to store RETURNING data,
         * although the FDW can return some other slot if it wants.
         */
        slot = ExecGetReturningSlot(estate, resultRelInfo);
        slot = resultRelInfo->ri_FdwRoutine->ExecForeignDelete(estate,
                                                               resultRelInfo,
                                                               slot,
                                                               context->planSlot);
 
        if (slot == NULL)       /* "do nothing" */
            return NULL;
 
        /*
         * RETURNING expressions might reference the tableoid column, so
         * (re)initialize tts_tableOid before evaluating them.
         */
        if (TTS_EMPTY(slot))
            ExecStoreAllNullTuple(slot);
 
        slot->tts_tableOid = RelationGetRelid(resultRelationDesc);
    }
    else
    {
        /*
         * delete the tuple
         *
         * Note: if context->estate->es_crosscheck_snapshot isn't
         * InvalidSnapshot, we check that the row to be deleted is visible to
         * that snapshot, and throw a can't-serialize error if not. This is a
         * special-case behavior needed for referential integrity updates in
         * transaction-snapshot mode transactions.
         */
ldelete:
        result = ExecDeleteAct(context, resultRelInfo, tupleid, changingPart);
 
        if (tmresult)
            *tmresult = result;
 
        switch (result)
        {
            case TM_SelfModified:
 
                /*
                 * The target tuple was already updated or deleted by the
                 * current command, or by a later command in the current
                 * transaction.  The former case is possible in a join DELETE
                 * where multiple tuples join to the same target tuple. This
                 * is somewhat questionable, but Postgres has always allowed
                 * it: we just ignore additional deletion attempts.
                 *
                 * The latter case arises if the tuple is modified by a
                 * command in a BEFORE trigger, or perhaps by a command in a
                 * volatile function used in the query.  In such situations we
                 * should not ignore the deletion, but it is equally unsafe to
                 * proceed.  We don't want to discard the original DELETE
                 * while keeping the triggered actions based on its deletion;
                 * and it would be no better to allow the original DELETE
                 * while discarding updates that it triggered.  The row update
                 * carries some information that might be important according
                 * to business rules; so throwing an error is the only safe
                 * course.
                 *
                 * If a trigger actually intends this type of interaction, it
                 * can re-execute the DELETE and then return NULL to cancel
                 * the outer delete.
                 */
                if (context->tmfd.cmax != estate->es_output_cid)
                    ereport(ERROR,
                            (errcode(ERRCODE_TRIGGERED_DATA_CHANGE_VIOLATION),
                             errmsg("tuple to be deleted was already modified by an operation triggered by the current command"),
                             errhint("Consider using an AFTER trigger instead of a BEFORE trigger to propagate changes to other rows.")));
 
                /* Else, already deleted by self; nothing to do */
                return NULL;
 
            case TM_Ok:
                break;
 
            case TM_Updated:
                {
                    TupleTableSlot *inputslot;
                    TupleTableSlot *epqslot;
 
                    if (IsolationUsesXactSnapshot())
                        ereport(ERROR,
                                (errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
                                 errmsg("could not serialize access due to concurrent update")));
 
                    /*
                     * Already know that we're going to need to do EPQ, so
                     * fetch tuple directly into the right slot.
                     */
                    EvalPlanQualBegin(context->epqstate);
                    inputslot = EvalPlanQualSlot(context->epqstate, resultRelationDesc,
                                                 resultRelInfo->ri_RangeTableIndex);
 
                    result = table_tuple_lock(resultRelationDesc, tupleid,
                                              estate->es_snapshot,
                                              inputslot, estate->es_output_cid,
                                              LockTupleExclusive, LockWaitBlock,
                                              TUPLE_LOCK_FLAG_FIND_LAST_VERSION,
                                              &context->tmfd);
 
                    switch (result)
                    {
                        case TM_Ok:
                            Assert(context->tmfd.traversed);
                            epqslot = EvalPlanQual(context->epqstate,
                                                   resultRelationDesc,
                                                   resultRelInfo->ri_RangeTableIndex,
                                                   inputslot);
                            if (TupIsNull(epqslot))
                                /* Tuple not passing quals anymore, exiting... */
                                return NULL;
 
                            /*
                             * If requested, skip delete and pass back the
                             * updated row.
                             */
                            if (epqreturnslot)
                            {
                                *epqreturnslot = epqslot;
                                return NULL;
                            }
                            else
                                goto ldelete;
 
                        case TM_SelfModified:
 
                            /*
                             * This can be reached when following an update
                             * chain from a tuple updated by another session,
                             * reaching a tuple that was already updated in
                             * this transaction. If previously updated by this
                             * command, ignore the delete, otherwise error
                             * out.
                             *
                             * See also TM_SelfModified response to
                             * table_tuple_delete() above.
                             */
                            if (context->tmfd.cmax != estate->es_output_cid)
                                ereport(ERROR,
                                        (errcode(ERRCODE_TRIGGERED_DATA_CHANGE_VIOLATION),
                                         errmsg("tuple to be deleted was already modified by an operation triggered by the current command"),
                                         errhint("Consider using an AFTER trigger instead of a BEFORE trigger to propagate changes to other rows.")));
                            return NULL;
 
                        case TM_Deleted:
                            /* tuple already deleted; nothing to do */
                            return NULL;
 
                        default:
 
                            /*
                             * TM_Invisible should be impossible because we're
                             * waiting for updated row versions, and would
                             * already have errored out if the first version
                             * is invisible.
                             *
                             * TM_Updated should be impossible, because we're
                             * locking the latest version via
                             * TUPLE_LOCK_FLAG_FIND_LAST_VERSION.
                             */
                            elog(ERROR, "unexpected table_tuple_lock status: %u",
                                 result);
                            return NULL;
                    }
 
                    Assert(false);
                    break;
                }
 
            case TM_Deleted:
                if (IsolationUsesXactSnapshot())
                    ereport(ERROR,
                            (errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
                             errmsg("could not serialize access due to concurrent delete")));
                /* tuple already deleted; nothing to do */
                return NULL;
 
            default:
                elog(ERROR, "unrecognized table_tuple_delete status: %u",
                     result);
                return NULL;
        }
 
        /*
         * Note: Normally one would think that we have to delete index tuples
         * associated with the heap tuple now...
         *
         * ... but in POSTGRES, we have no need to do this because VACUUM will
         * take care of it later.  We can't delete index tuples immediately
         * anyway, since the tuple is still visible to other transactions.
         */
    }
 
    if (canSetTag)
        (estate->es_processed)++;
 
    /* Tell caller that the delete actually happened. */
    if (tupleDeleted)
        *tupleDeleted = true;
 
    ExecDeleteEpilogue(context, resultRelInfo, tupleid, oldtuple, changingPart);
 
    /*
     * Process RETURNING if present and if requested.
     *
     * If this is part of a cross-partition UPDATE, and the RETURNING list
     * refers to any OLD column values, save the old tuple here for later
     * processing of the RETURNING list by ExecInsert().
     */
    saveOld = changingPart && resultRelInfo->ri_projectReturning &&
        resultRelInfo->ri_projectReturning->pi_state.flags & EEO_FLAG_HAS_OLD;
 
    if (resultRelInfo->ri_projectReturning && (processReturning || saveOld))
    {
        /*
         * We have to put the target tuple into a slot, which means first we
         * gotta fetch it.  We can use the trigger tuple slot.
         */
        TupleTableSlot *rslot;
 
        if (resultRelInfo->ri_FdwRoutine)
        {
            /* FDW must have provided a slot containing the deleted row */
            Assert(!TupIsNull(slot));
        }
        else
        {
            slot = ExecGetReturningSlot(estate, resultRelInfo);
            if (oldtuple != NULL)
            {
                ExecForceStoreHeapTuple(oldtuple, slot, false);
            }
            else
            {
                if (!table_tuple_fetch_row_version(resultRelationDesc, tupleid,
                                                   SnapshotAny, slot))
                    elog(ERROR, "failed to fetch deleted tuple for DELETE RETURNING");
            }
        }
 
        /*
         * If required, save the old tuple for later processing of the
         * RETURNING list by ExecInsert().
         */
        if (saveOld)
        {
            TupleConversionMap *tupconv_map;
 
            /*
             * Convert the tuple into the root partition's format/slot, if
             * needed.  ExecInsert() will then convert it to the new
             * partition's format/slot, if necessary.
             */
            tupconv_map = ExecGetChildToRootMap(resultRelInfo);
            if (tupconv_map != NULL)
            {
                ResultRelInfo *rootRelInfo = context->mtstate->rootResultRelInfo;
                TupleTableSlot *oldSlot = slot;
 
                slot = execute_attr_map_slot(tupconv_map->attrMap,
                                             slot,
                                             ExecGetReturningSlot(estate,
                                                                  rootRelInfo));
 
                slot->tts_tableOid = oldSlot->tts_tableOid;
                ItemPointerCopy(&oldSlot->tts_tid, &slot->tts_tid);
            }
 
            context->cpDeletedSlot = slot;
 
            return NULL;
        }
 
        rslot = ExecProcessReturning(context, resultRelInfo, true,
                                     slot, NULL, context->planSlot);
 
        /*
         * Before releasing the target tuple again, make sure rslot has a
         * local copy of any pass-by-reference values.
         */
        ExecMaterializeSlot(rslot);
 
        ExecClearTuple(slot);
 
        return rslot;
    }
 
    return NULL;
}
 
/*
 * ExecCrossPartitionUpdate --- Move an updated tuple to another partition.
 *
 * This works by first deleting the old tuple from the current partition,
 * followed by inserting the new tuple into the root parent table, that is,
 * mtstate->rootResultRelInfo.  It will be re-routed from there to the
 * correct partition.
 *
 * Returns true if the tuple has been successfully moved, or if it's found
 * that the tuple was concurrently deleted so there's nothing more to do
 * for the caller.
 *
 * False is returned if the tuple we're trying to move is found to have been
 * concurrently updated.  In that case, the caller must check if the updated
 * tuple that's returned in *retry_slot still needs to be re-routed, and call
 * this function again or perform a regular update accordingly.  For MERGE,
 * the updated tuple is not returned in *retry_slot; it has its own retry
 * logic.
 */
static bool
ExecCrossPartitionUpdate(ModifyTableContext *context,
                         ResultRelInfo *resultRelInfo,
                         ItemPointer tupleid, HeapTuple oldtuple,
                         TupleTableSlot *slot,
                         bool canSetTag,
                         UpdateContext *updateCxt,
                         TM_Result *tmresult,
                         TupleTableSlot **retry_slot,
                         TupleTableSlot **inserted_tuple,
                         ResultRelInfo **insert_destrel)
{
    ModifyTableState *mtstate = context->mtstate;
    EState     *estate = mtstate->ps.state;
    TupleConversionMap *tupconv_map;
    bool        tuple_deleted;
    TupleTableSlot *epqslot = NULL;
 
    context->cpDeletedSlot = NULL;
    context->cpUpdateReturningSlot = NULL;
    *retry_slot = NULL;
 
    /*
     * Disallow an INSERT ON CONFLICT DO UPDATE that causes the original row
     * to migrate to a different partition.  Maybe this can be implemented
     * some day, but it seems a fringe feature with little redeeming value.
     */
    if (((ModifyTable *) mtstate->ps.plan)->onConflictAction == ONCONFLICT_UPDATE)
        ereport(ERROR,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg("invalid ON UPDATE specification"),
                 errdetail("The result tuple would appear in a different partition than the original tuple.")));
 
    /*
     * When an UPDATE is run directly on a leaf partition, simply fail with a
     * partition constraint violation error.
     */
    if (resultRelInfo == mtstate->rootResultRelInfo)
        ExecPartitionCheckEmitError(resultRelInfo, slot, estate);
 
    /*
     * Initialize tuple routing info if not already done. Note whatever we do
     * here must be done in ExecInitModifyTable for FOR PORTION OF as well.
     */
    if (mtstate->mt_partition_tuple_routing == NULL)
    {
        Relation    rootRel = mtstate->rootResultRelInfo->ri_RelationDesc;
        MemoryContext oldcxt;
 
        /* Things built here have to last for the query duration. */
        oldcxt = MemoryContextSwitchTo(estate->es_query_cxt);
 
        mtstate->mt_partition_tuple_routing =
            ExecSetupPartitionTupleRouting(estate, rootRel);
 
        /*
         * Before a partition's tuple can be re-routed, it must first be
         * converted to the root's format, so we'll need a slot for storing
         * such tuples.
         */
        Assert(mtstate->mt_root_tuple_slot == NULL);
        mtstate->mt_root_tuple_slot = table_slot_create(rootRel, NULL);
 
        MemoryContextSwitchTo(oldcxt);
    }
 
    /*
     * Row movement, part 1.  Delete the tuple, but skip RETURNING processing.
     * We want to return rows from INSERT.
     */
    ExecDelete(context, resultRelInfo,
               tupleid, oldtuple,
               false,           /* processReturning */
               true,            /* changingPart */
               false,           /* canSetTag */
               tmresult, &tuple_deleted, &epqslot);
 
    /*
     * For some reason if DELETE didn't happen (e.g. trigger prevented it, or
     * it was already deleted by self, or it was concurrently deleted by
     * another transaction), then we should skip the insert as well;
     * otherwise, an UPDATE could cause an increase in the total number of
     * rows across all partitions, which is clearly wrong.
     *
     * For a normal UPDATE, the case where the tuple has been the subject of a
     * concurrent UPDATE or DELETE would be handled by the EvalPlanQual
     * machinery, but for an UPDATE that we've translated into a DELETE from
     * this partition and an INSERT into some other partition, that's not
     * available, because CTID chains can't span relation boundaries.  We
     * mimic the semantics to a limited extent by skipping the INSERT if the
     * DELETE fails to find a tuple.  This ensures that two concurrent
     * attempts to UPDATE the same tuple at the same time can't turn one tuple
     * into two, and that an UPDATE of a just-deleted tuple can't resurrect
     * it.
     */
    if (!tuple_deleted)
    {
        /*
         * epqslot will be typically NULL.  But when ExecDelete() finds that
         * another transaction has concurrently updated the same row, it
         * re-fetches the row, skips the delete, and epqslot is set to the
         * re-fetched tuple slot.  In that case, we need to do all the checks
         * again.  For MERGE, we leave everything to the caller (it must do
         * additional rechecking, and might end up executing a different
         * action entirely).
         */
        if (mtstate->operation == CMD_MERGE)
            return *tmresult == TM_Ok;
        else if (TupIsNull(epqslot))
            return true;
        else
        {
            /* Fetch the most recent version of old tuple. */
            TupleTableSlot *oldSlot;
 
            /* ... but first, make sure ri_oldTupleSlot is initialized. */
            if (unlikely(!resultRelInfo->ri_projectNewInfoValid))
                ExecInitUpdateProjection(mtstate, resultRelInfo);
            oldSlot = resultRelInfo->ri_oldTupleSlot;
            if (!table_tuple_fetch_row_version(resultRelInfo->ri_RelationDesc,
                                               tupleid,
                                               SnapshotAny,
                                               oldSlot))
                elog(ERROR, "failed to fetch tuple being updated");
            /* and project the new tuple to retry the UPDATE with */
            *retry_slot = ExecGetUpdateNewTuple(resultRelInfo, epqslot,
                                                oldSlot);
            return false;
        }
    }
 
    /*
     * resultRelInfo is one of the per-relation resultRelInfos.  So we should
     * convert the tuple into root's tuple descriptor if needed, since
     * ExecInsert() starts the search from root.
     */
    tupconv_map = ExecGetChildToRootMap(resultRelInfo);
    if (tupconv_map != NULL)
        slot = execute_attr_map_slot(tupconv_map->attrMap,
                                     slot,
                                     mtstate->mt_root_tuple_slot);
 
    /* Tuple routing starts from the root table. */
    context->cpUpdateReturningSlot =
        ExecInsert(context, mtstate->rootResultRelInfo, slot, canSetTag,
                   inserted_tuple, insert_destrel);
 
    /*
     * Reset the transition state that may possibly have been written by
     * INSERT.
     */
    if (mtstate->mt_transition_capture)
        mtstate->mt_transition_capture->tcs_original_insert_tuple = NULL;
 
    /* We're done moving. */
    return true;
}
 
/*
 * ExecUpdatePrologue -- subroutine for ExecUpdate
 *
 * Prepare executor state for UPDATE.  This includes running BEFORE ROW
 * triggers.  We return false if one of them makes the update a no-op;
 * otherwise, return true.
 */
static bool
ExecUpdatePrologue(ModifyTableContext *context, ResultRelInfo *resultRelInfo,
                   ItemPointer tupleid, HeapTuple oldtuple, TupleTableSlot *slot,
                   TM_Result *result)
{
    Relation    resultRelationDesc = resultRelInfo->ri_RelationDesc;
 
    if (result)
        *result = TM_Ok;
 
    ExecMaterializeSlot(slot);
 
    /*
     * Open the table's indexes, if we have not done so already, so that we
     * can add new index entries for the updated tuple.
     */
    if (resultRelationDesc->rd_rel->relhasindex &&
        resultRelInfo->ri_IndexRelationDescs == NULL)
        ExecOpenIndices(resultRelInfo, false);
 
    /* BEFORE ROW UPDATE triggers */
    if (resultRelInfo->ri_TrigDesc &&
        resultRelInfo->ri_TrigDesc->trig_update_before_row)
    {
        /* Flush any pending inserts, so rows are visible to the triggers */
        if (context->estate->es_insert_pending_result_relations != NIL)
            ExecPendingInserts(context->estate);
 
        return ExecBRUpdateTriggers(context->estate, context->epqstate,
                                    resultRelInfo, tupleid, oldtuple, slot,
                                    result, &context->tmfd,
                                    context->mtstate->operation == CMD_MERGE);
    }
 
    return true;
}
 
/*
 * ExecUpdatePrepareSlot -- subroutine for ExecUpdateAct
 *
 * Apply the final modifications to the tuple slot before the update.
 * (This is split out because we also need it in the foreign-table code path.)
 */
static void
ExecUpdatePrepareSlot(ResultRelInfo *resultRelInfo,
                      TupleTableSlot *slot,
                      EState *estate)
{
    Relation    resultRelationDesc = resultRelInfo->ri_RelationDesc;
 
    /*
     * Constraints and GENERATED expressions might reference the tableoid
     * column, so (re-)initialize tts_tableOid before evaluating them.
     */
    slot->tts_tableOid = RelationGetRelid(resultRelationDesc);
 
    /*
     * Compute stored generated columns
     */
    if (resultRelationDesc->rd_att->constr &&
        resultRelationDesc->rd_att->constr->has_generated_stored)
        ExecComputeStoredGenerated(resultRelInfo, estate, slot,
                                   CMD_UPDATE);
}
 
/*
 * ExecUpdateAct -- subroutine for ExecUpdate
 *
 * Actually update the tuple, when operating on a plain table.  If the
 * table is a partition, and the command was called referencing an ancestor
 * partitioned table, this routine migrates the resulting tuple to another
 * partition.
 *
 * The caller is in charge of keeping indexes current as necessary.  The
 * caller is also in charge of doing EvalPlanQual if the tuple is found to
 * be concurrently updated.  However, in case of a cross-partition update,
 * this routine does it.
 */
static TM_Result
ExecUpdateAct(ModifyTableContext *context, ResultRelInfo *resultRelInfo,
              ItemPointer tupleid, HeapTuple oldtuple, TupleTableSlot *slot,
              bool canSetTag, UpdateContext *updateCxt)
{
    EState     *estate = context->estate;
    Relation    resultRelationDesc = resultRelInfo->ri_RelationDesc;
    bool        partition_constraint_failed;
    TM_Result   result;
 
    updateCxt->crossPartUpdate = false;
 
    /*
     * If we move the tuple to a new partition, we loop back here to recompute
     * GENERATED values (which are allowed to be different across partitions)
     * and recheck any RLS policies and constraints.  We do not fire any
     * BEFORE triggers of the new partition, however.
     */
lreplace:
    /* Fill in GENERATEd columns */
    ExecUpdatePrepareSlot(resultRelInfo, slot, estate);
 
    /* ensure slot is independent, consider e.g. EPQ */
    ExecMaterializeSlot(slot);
 
    /*
     * If partition constraint fails, this row might get moved to another
     * partition, in which case we should check the RLS CHECK policy just
     * before inserting into the new partition, rather than doing it here.
     * This is because a trigger on that partition might again change the row.
     * So skip the WCO checks if the partition constraint fails.
     */
    partition_constraint_failed =
        resultRelationDesc->rd_rel->relispartition &&
        !ExecPartitionCheck(resultRelInfo, slot, estate, false);
 
    /* Check any RLS UPDATE WITH CHECK policies */
    if (!partition_constraint_failed &&
        resultRelInfo->ri_WithCheckOptions != NIL)
    {
        /*
         * ExecWithCheckOptions() will skip any WCOs which are not of the kind
         * we are looking for at this point.
         */
        ExecWithCheckOptions(WCO_RLS_UPDATE_CHECK,
                             resultRelInfo, slot, estate);
    }
 
    /*
     * If a partition check failed, try to move the row into the right
     * partition.
     */
    if (partition_constraint_failed)
    {
        TupleTableSlot *inserted_tuple,
                   *retry_slot;
        ResultRelInfo *insert_destrel = NULL;
 
        /*
         * ExecCrossPartitionUpdate will first DELETE the row from the
         * partition it's currently in and then insert it back into the root
         * table, which will re-route it to the correct partition.  However,
         * if the tuple has been concurrently updated, a retry is needed.
         */
        if (ExecCrossPartitionUpdate(context, resultRelInfo,
                                     tupleid, oldtuple, slot,
                                     canSetTag, updateCxt,
                                     &result,
                                     &retry_slot,
                                     &inserted_tuple,
                                     &insert_destrel))
        {
            /* success! */
            updateCxt->crossPartUpdate = true;
 
            /*
             * If the partitioned table being updated is referenced in foreign
             * keys, queue up trigger events to check that none of them were
             * violated.  No special treatment is needed in
             * non-cross-partition update situations, because the leaf
             * partition's AR update triggers will take care of that.  During
             * cross-partition updates implemented as delete on the source
             * partition followed by insert on the destination partition,
             * AR-UPDATE triggers of the root table (that is, the table
             * mentioned in the query) must be fired.
             *
             * NULL insert_destrel means that the move failed to occur, that
             * is, the update failed, so no need to anything in that case.
             */
            if (insert_destrel &&
                resultRelInfo->ri_TrigDesc &&
                resultRelInfo->ri_TrigDesc->trig_update_after_row)
                ExecCrossPartitionUpdateForeignKey(context,
                                                   resultRelInfo,
                                                   insert_destrel,
                                                   tupleid, slot,
                                                   inserted_tuple);
 
            return TM_Ok;
        }
 
        /*
         * No luck, a retry is needed.  If running MERGE, we do not do so
         * here; instead let it handle that on its own rules.
         */
        if (context->mtstate->operation == CMD_MERGE)
            return result;
 
        /*
         * ExecCrossPartitionUpdate installed an updated version of the new
         * tuple in the retry slot; start over.
         */
        slot = retry_slot;
        goto lreplace;
    }
 
    /*
     * Check the constraints of the tuple.  We've already checked the
     * partition constraint above; however, we must still ensure the tuple
     * passes all other constraints, so we will call ExecConstraints() and
     * have it validate all remaining checks.
     */
    if (resultRelationDesc->rd_att->constr)
        ExecConstraints(resultRelInfo, slot, estate);
 
    /*
     * replace the heap tuple
     *
     * Note: if es_crosscheck_snapshot isn't InvalidSnapshot, we check that
     * the row to be updated is visible to that snapshot, and throw a
     * can't-serialize error if not. This is a special-case behavior needed
     * for referential integrity updates in transaction-snapshot mode
     * transactions.
     */
    result = table_tuple_update(resultRelationDesc, tupleid, slot,
                                estate->es_output_cid,
                                0,
                                estate->es_snapshot,
                                estate->es_crosscheck_snapshot,
                                true /* wait for commit */ ,
                                &context->tmfd, &updateCxt->lockmode,
                                &updateCxt->updateIndexes);
 
    return result;
}
 
/*
 * ExecUpdateEpilogue -- subroutine for ExecUpdate
 *
 * Closing steps of updating a tuple.  Must be called if ExecUpdateAct
 * returns indicating that the tuple was updated. It also inserts temporal
 * leftovers from an UPDATE FOR PORTION OF.
 */
static void
ExecUpdateEpilogue(ModifyTableContext *context, UpdateContext *updateCxt,
                   ResultRelInfo *resultRelInfo, ItemPointer tupleid,
                   HeapTuple oldtuple, TupleTableSlot *slot)
{
    ModifyTableState *mtstate = context->mtstate;
    List       *recheckIndexes = NIL;
 
    /* insert index entries for tuple if necessary */
    if (resultRelInfo->ri_NumIndices > 0 && (updateCxt->updateIndexes != TU_None))
    {
        uint32      flags = EIIT_IS_UPDATE;
 
        if (updateCxt->updateIndexes == TU_Summarizing)
            flags |= EIIT_ONLY_SUMMARIZING;
        recheckIndexes = ExecInsertIndexTuples(resultRelInfo, context->estate,
                                               flags, slot, NIL,
                                               NULL);
    }
 
    /* Compute temporal leftovers in FOR PORTION OF */
    if (((ModifyTable *) context->mtstate->ps.plan)->forPortionOf)
        ExecForPortionOfLeftovers(context, context->estate, resultRelInfo, tupleid);
 
    /* AFTER ROW UPDATE Triggers */
    ExecARUpdateTriggers(context->estate, resultRelInfo,
                         NULL, NULL,
                         tupleid, oldtuple, slot,
                         recheckIndexes,
                         mtstate->operation == CMD_INSERT ?
                         mtstate->mt_oc_transition_capture :
                         mtstate->mt_transition_capture,
                         false);
 
    list_free(recheckIndexes);
 
    /*
     * Check any WITH CHECK OPTION constraints from parent views.  We are
     * required to do this after testing all constraints and uniqueness
     * violations per the SQL spec, so we do it after actually updating the
     * record in the heap and all indexes.
     *
     * ExecWithCheckOptions() will skip any WCOs which are not of the kind we
     * are looking for at this point.
     */
    if (resultRelInfo->ri_WithCheckOptions != NIL)
        ExecWithCheckOptions(WCO_VIEW_CHECK, resultRelInfo,
                             slot, context->estate);
}
 
/*
 * Queues up an update event using the target root partitioned table's
 * trigger to check that a cross-partition update hasn't broken any foreign
 * keys pointing into it.
 */
static void
ExecCrossPartitionUpdateForeignKey(ModifyTableContext *context,
                                   ResultRelInfo *sourcePartInfo,
                                   ResultRelInfo *destPartInfo,
                                   ItemPointer tupleid,
                                   TupleTableSlot *oldslot,
                                   TupleTableSlot *newslot)
{
    ListCell   *lc;
    ResultRelInfo *rootRelInfo;
    List       *ancestorRels;
 
    rootRelInfo = sourcePartInfo->ri_RootResultRelInfo;
    ancestorRels = ExecGetAncestorResultRels(context->estate, sourcePartInfo);
 
    /*
     * For any foreign keys that point directly into a non-root ancestors of
     * the source partition, we can in theory fire an update event to enforce
     * those constraints using their triggers, if we could tell that both the
     * source and the destination partitions are under the same ancestor. But
     * for now, we simply report an error that those cannot be enforced.
     */
    foreach(lc, ancestorRels)
    {
        ResultRelInfo *rInfo = lfirst(lc);
        TriggerDesc *trigdesc = rInfo->ri_TrigDesc;
        bool        has_noncloned_fkey = false;
 
        /* Root ancestor's triggers will be processed. */
        if (rInfo == rootRelInfo)
            continue;
 
        if (trigdesc && trigdesc->trig_update_after_row)
        {
            for (int i = 0; i < trigdesc->numtriggers; i++)
            {
                Trigger    *trig = &trigdesc->triggers[i];
 
                if (!trig->tgisclone &&
                    RI_FKey_trigger_type(trig->tgfoid) == RI_TRIGGER_PK)
                {
                    has_noncloned_fkey = true;
                    break;
                }
            }
        }
 
        if (has_noncloned_fkey)
            ereport(ERROR,
                    (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                     errmsg("cannot move tuple across partitions when a non-root ancestor of the source partition is directly referenced in a foreign key"),
                     errdetail("A foreign key points to ancestor \"%s\" but not the root ancestor \"%s\".",
                               RelationGetRelationName(rInfo->ri_RelationDesc),
                               RelationGetRelationName(rootRelInfo->ri_RelationDesc)),
                     errhint("Consider defining the foreign key on table \"%s\".",
                             RelationGetRelationName(rootRelInfo->ri_RelationDesc))));
    }
 
    /* Perform the root table's triggers. */
    ExecARUpdateTriggers(context->estate,
                         rootRelInfo, sourcePartInfo, destPartInfo,
                         tupleid, NULL, newslot, NIL, NULL, true);
}
 
/* ----------------------------------------------------------------
 *      ExecUpdate
 *
 *      note: we can't run UPDATE queries with transactions
 *      off because UPDATEs are actually INSERTs and our
 *      scan will mistakenly loop forever, updating the tuple
 *      it just inserted..  This should be fixed but until it
 *      is, we don't want to get stuck in an infinite loop
 *      which corrupts your database..
 *
 *      When updating a table, tupleid identifies the tuple to update and
 *      oldtuple is NULL.  When updating through a view INSTEAD OF trigger,
 *      oldtuple is passed to the triggers and identifies what to update, and
 *      tupleid is invalid.  When updating a foreign table, tupleid is
 *      invalid; the FDW has to figure out which row to update using data from
 *      the planSlot.  oldtuple is passed to foreign table triggers; it is
 *      NULL when the foreign table has no relevant triggers.
 *
 *      oldSlot contains the old tuple value.
 *      slot contains the new tuple value to be stored.
 *      planSlot is the output of the ModifyTable's subplan; we use it
 *      to access values from other input tables (for RETURNING),
 *      row-ID junk columns, etc.
 *
 *      Returns RETURNING result if any, otherwise NULL.  On exit, if tupleid
 *      had identified the tuple to update, it will identify the tuple
 *      actually updated after EvalPlanQual.
 * ----------------------------------------------------------------
 */
static TupleTableSlot *
ExecUpdate(ModifyTableContext *context, ResultRelInfo *resultRelInfo,
           ItemPointer tupleid, HeapTuple oldtuple, TupleTableSlot *oldSlot,
           TupleTableSlot *slot, bool canSetTag)
{
    EState     *estate = context->estate;
    Relation    resultRelationDesc = resultRelInfo->ri_RelationDesc;
    UpdateContext updateCxt = {0};
    TM_Result   result;
 
    /*
     * abort the operation if not running transactions
     */
    if (IsBootstrapProcessingMode())
        elog(ERROR, "cannot UPDATE during bootstrap");
 
    /*
     * Prepare for the update.  This includes BEFORE ROW triggers, so we're
     * done if it says we are.
     */
    if (!ExecUpdatePrologue(context, resultRelInfo, tupleid, oldtuple, slot, NULL))
        return NULL;
 
    /* INSTEAD OF ROW UPDATE Triggers */
    if (resultRelInfo->ri_TrigDesc &&
        resultRelInfo->ri_TrigDesc->trig_update_instead_row)
    {
        if (!ExecIRUpdateTriggers(estate, resultRelInfo,
                                  oldtuple, slot))
            return NULL;        /* "do nothing" */
    }
    else if (resultRelInfo->ri_FdwRoutine)
    {
        /* Fill in GENERATEd columns */
        ExecUpdatePrepareSlot(resultRelInfo, slot, estate);
 
        /*
         * update in foreign table: let the FDW do it
         */
        slot = resultRelInfo->ri_FdwRoutine->ExecForeignUpdate(estate,
                                                               resultRelInfo,
                                                               slot,
                                                               context->planSlot);
 
        if (slot == NULL)       /* "do nothing" */
            return NULL;
 
        /*
         * AFTER ROW Triggers or RETURNING expressions might reference the
         * tableoid column, so (re-)initialize tts_tableOid before evaluating
         * them.  (This covers the case where the FDW replaced the slot.)
         */
        slot->tts_tableOid = RelationGetRelid(resultRelationDesc);
    }
    else
    {
        ItemPointerData lockedtid;
 
        /*
         * If we generate a new candidate tuple after EvalPlanQual testing, we
         * must loop back here to try again.  (We don't need to redo triggers,
         * however.  If there are any BEFORE triggers then trigger.c will have
         * done table_tuple_lock to lock the correct tuple, so there's no need
         * to do them again.)
         */
redo_act:
        lockedtid = *tupleid;
        result = ExecUpdateAct(context, resultRelInfo, tupleid, oldtuple, slot,
                               canSetTag, &updateCxt);
 
        /*
         * If ExecUpdateAct reports that a cross-partition update was done,
         * then the RETURNING tuple (if any) has been projected and there's
         * nothing else for us to do.
         */
        if (updateCxt.crossPartUpdate)
            return context->cpUpdateReturningSlot;
 
        switch (result)
        {
            case TM_SelfModified:
 
                /*
                 * The target tuple was already updated or deleted by the
                 * current command, or by a later command in the current
                 * transaction.  The former case is possible in a join UPDATE
                 * where multiple tuples join to the same target tuple. This
                 * is pretty questionable, but Postgres has always allowed it:
                 * we just execute the first update action and ignore
                 * additional update attempts.
                 *
                 * The latter case arises if the tuple is modified by a
                 * command in a BEFORE trigger, or perhaps by a command in a
                 * volatile function used in the query.  In such situations we
                 * should not ignore the update, but it is equally unsafe to
                 * proceed.  We don't want to discard the original UPDATE
                 * while keeping the triggered actions based on it; and we
                 * have no principled way to merge this update with the
                 * previous ones.  So throwing an error is the only safe
                 * course.
                 *
                 * If a trigger actually intends this type of interaction, it
                 * can re-execute the UPDATE (assuming it can figure out how)
                 * and then return NULL to cancel the outer update.
                 */
                if (context->tmfd.cmax != estate->es_output_cid)
                    ereport(ERROR,
                            (errcode(ERRCODE_TRIGGERED_DATA_CHANGE_VIOLATION),
                             errmsg("tuple to be updated was already modified by an operation triggered by the current command"),
                             errhint("Consider using an AFTER trigger instead of a BEFORE trigger to propagate changes to other rows.")));
 
                /* Else, already updated by self; nothing to do */
                return NULL;
 
            case TM_Ok:
                break;
 
            case TM_Updated:
                {
                    TupleTableSlot *inputslot;
                    TupleTableSlot *epqslot;
 
                    if (IsolationUsesXactSnapshot())
                        ereport(ERROR,
                                (errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
                                 errmsg("could not serialize access due to concurrent update")));
 
                    /*
                     * Already know that we're going to need to do EPQ, so
                     * fetch tuple directly into the right slot.
                     */
                    inputslot = EvalPlanQualSlot(context->epqstate, resultRelationDesc,
                                                 resultRelInfo->ri_RangeTableIndex);
 
                    result = table_tuple_lock(resultRelationDesc, tupleid,
                                              estate->es_snapshot,
                                              inputslot, estate->es_output_cid,
                                              updateCxt.lockmode, LockWaitBlock,
                                              TUPLE_LOCK_FLAG_FIND_LAST_VERSION,
                                              &context->tmfd);
 
                    switch (result)
                    {
                        case TM_Ok:
                            Assert(context->tmfd.traversed);
 
                            epqslot = EvalPlanQual(context->epqstate,
                                                   resultRelationDesc,
                                                   resultRelInfo->ri_RangeTableIndex,
                                                   inputslot);
                            if (TupIsNull(epqslot))
                                /* Tuple not passing quals anymore, exiting... */
                                return NULL;
 
                            /* Make sure ri_oldTupleSlot is initialized. */
                            if (unlikely(!resultRelInfo->ri_projectNewInfoValid))
                                ExecInitUpdateProjection(context->mtstate,
                                                         resultRelInfo);
 
                            if (resultRelInfo->ri_needLockTagTuple)
                            {
                                UnlockTuple(resultRelationDesc,
                                            &lockedtid, InplaceUpdateTupleLock);
                                LockTuple(resultRelationDesc,
                                          tupleid, InplaceUpdateTupleLock);
                            }
 
                            /* Fetch the most recent version of old tuple. */
                            oldSlot = resultRelInfo->ri_oldTupleSlot;
                            if (!table_tuple_fetch_row_version(resultRelationDesc,
                                                               tupleid,
                                                               SnapshotAny,
                                                               oldSlot))
                                elog(ERROR, "failed to fetch tuple being updated");
                            slot = ExecGetUpdateNewTuple(resultRelInfo,
                                                         epqslot, oldSlot);
                            goto redo_act;
 
                        case TM_Deleted:
                            /* tuple already deleted; nothing to do */
                            return NULL;
 
                        case TM_SelfModified:
 
                            /*
                             * This can be reached when following an update
                             * chain from a tuple updated by another session,
                             * reaching a tuple that was already updated in
                             * this transaction. If previously modified by
                             * this command, ignore the redundant update,
                             * otherwise error out.
                             *
                             * See also TM_SelfModified response to
                             * table_tuple_update() above.
                             */
                            if (context->tmfd.cmax != estate->es_output_cid)
                                ereport(ERROR,
                                        (errcode(ERRCODE_TRIGGERED_DATA_CHANGE_VIOLATION),
                                         errmsg("tuple to be updated was already modified by an operation triggered by the current command"),
                                         errhint("Consider using an AFTER trigger instead of a BEFORE trigger to propagate changes to other rows.")));
                            return NULL;
 
                        default:
                            /* see table_tuple_lock call in ExecDelete() */
                            elog(ERROR, "unexpected table_tuple_lock status: %u",
                                 result);
                            return NULL;
                    }
                }
 
                break;
 
            case TM_Deleted:
                if (IsolationUsesXactSnapshot())
                    ereport(ERROR,
                            (errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
                             errmsg("could not serialize access due to concurrent delete")));
                /* tuple already deleted; nothing to do */
                return NULL;
 
            default:
                elog(ERROR, "unrecognized table_tuple_update status: %u",
                     result);
                return NULL;
        }
    }
 
    if (canSetTag)
        (estate->es_processed)++;
 
    ExecUpdateEpilogue(context, &updateCxt, resultRelInfo, tupleid, oldtuple,
                       slot);
 
    /* Process RETURNING if present */
    if (resultRelInfo->ri_projectReturning)
        return ExecProcessReturning(context, resultRelInfo, false,
                                    oldSlot, slot, context->planSlot);
 
    return NULL;
}
 
/*
 * ExecOnConflictLockRow --- lock the row for ON CONFLICT DO SELECT/UPDATE
 *
 * Try to lock tuple for update as part of speculative insertion for ON
 * CONFLICT DO UPDATE or ON CONFLICT DO SELECT FOR UPDATE/SHARE.
 *
 * Returns true if the row is successfully locked, or false if the caller must
 * retry the INSERT from scratch.
 */
static bool
ExecOnConflictLockRow(ModifyTableContext *context,
                      TupleTableSlot *existing,
                      ItemPointer conflictTid,
                      Relation relation,
                      LockTupleMode lockmode,
                      bool isUpdate)
{
    TM_FailureData tmfd;
    TM_Result   test;
    Datum       xminDatum;
    TransactionId xmin;
    bool        isnull;
 
    /*
     * Lock tuple with lockmode.  Don't follow updates when tuple cannot be
     * locked without doing so.  A row locking conflict here means our
     * previous conclusion that the tuple is conclusively committed is not
     * true anymore.
     */
    test = table_tuple_lock(relation, conflictTid,
                            context->estate->es_snapshot,
                            existing, context->estate->es_output_cid,
                            lockmode, LockWaitBlock, 0,
                            &tmfd);
    switch (test)
    {
        case TM_Ok:
            /* success! */
            break;
 
        case TM_Invisible:
 
            /*
             * This can occur when a just inserted tuple is updated again in
             * the same command. E.g. because multiple rows with the same
             * conflicting key values are inserted.
             *
             * This is somewhat similar to the ExecUpdate() TM_SelfModified
             * case.  We do not want to proceed because it would lead to the
             * same row being updated a second time in some unspecified order,
             * and in contrast to plain UPDATEs there's no historical behavior
             * to break.
             *
             * It is the user's responsibility to prevent this situation from
             * occurring.  These problems are why the SQL standard similarly
             * specifies that for SQL MERGE, an exception must be raised in
             * the event of an attempt to update the same row twice.
             */
            xminDatum = slot_getsysattr(existing,
                                        MinTransactionIdAttributeNumber,
                                        &isnull);
            Assert(!isnull);
            xmin = DatumGetTransactionId(xminDatum);
 
            if (TransactionIdIsCurrentTransactionId(xmin))
                ereport(ERROR,
                        (errcode(ERRCODE_CARDINALITY_VIOLATION),
                /* translator: %s is a SQL command name */
                         errmsg("%s command cannot affect row a second time",
                                isUpdate ? "ON CONFLICT DO UPDATE" : "ON CONFLICT DO SELECT"),
                         errhint("Ensure that no rows proposed for insertion within the same command have duplicate constrained values.")));
 
            /* This shouldn't happen */
            elog(ERROR, "attempted to lock invisible tuple");
            break;
 
        case TM_SelfModified:
 
            /*
             * This state should never be reached. As a dirty snapshot is used
             * to find conflicting tuples, speculative insertion wouldn't have
             * seen this row to conflict with.
             */
            elog(ERROR, "unexpected self-updated tuple");
            break;
 
        case TM_Updated:
            if (IsolationUsesXactSnapshot())
                ereport(ERROR,
                        (errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
                         errmsg("could not serialize access due to concurrent update")));
 
            /*
             * Tell caller to try again from the very start.
             *
             * It does not make sense to use the usual EvalPlanQual() style
             * loop here, as the new version of the row might not conflict
             * anymore, or the conflicting tuple has actually been deleted.
             */
            ExecClearTuple(existing);
            return false;
 
        case TM_Deleted:
            if (IsolationUsesXactSnapshot())
                ereport(ERROR,
                        (errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
                         errmsg("could not serialize access due to concurrent delete")));
 
            /* see TM_Updated case */
            ExecClearTuple(existing);
            return false;
 
        default:
            elog(ERROR, "unrecognized table_tuple_lock status: %u", test);
    }
 
    /* Success, the tuple is locked. */
    return true;
}
 
/*
 * ExecOnConflictUpdate --- execute UPDATE of INSERT ON CONFLICT DO UPDATE
 *
 * Try to lock tuple for update as part of speculative insertion.  If
 * a qual originating from ON CONFLICT DO UPDATE is satisfied, update
 * (but still lock row, even though it may not satisfy estate's
 * snapshot).
 *
 * Returns true if we're done (with or without an update), or false if
 * the caller must retry the INSERT from scratch.
 */
static bool
ExecOnConflictUpdate(ModifyTableContext *context,
                     ResultRelInfo *resultRelInfo,
                     ItemPointer conflictTid,
                     TupleTableSlot *excludedSlot,
                     bool canSetTag,
                     TupleTableSlot **returning)
{
    ModifyTableState *mtstate = context->mtstate;
    ExprContext *econtext = mtstate->ps.ps_ExprContext;
    Relation    relation = resultRelInfo->ri_RelationDesc;
    ExprState  *onConflictSetWhere = resultRelInfo->ri_onConflict->oc_WhereClause;
    TupleTableSlot *existing = resultRelInfo->ri_onConflict->oc_Existing;
    LockTupleMode lockmode;
 
    /*
     * Parse analysis should have blocked ON CONFLICT for all system
     * relations, which includes these.  There's no fundamental obstacle to
     * supporting this; we'd just need to handle LOCKTAG_TUPLE like the other
     * ExecUpdate() caller.
     */
    Assert(!resultRelInfo->ri_needLockTagTuple);
 
    /* Determine lock mode to use */
    lockmode = ExecUpdateLockMode(context->estate, resultRelInfo);
 
    /* Lock tuple for update */
    if (!ExecOnConflictLockRow(context, existing, conflictTid,
                               resultRelInfo->ri_RelationDesc, lockmode, true))
        return false;
 
    /*
     * Verify that the tuple is visible to our MVCC snapshot if the current
     * isolation level mandates that.
     *
     * It's not sufficient to rely on the check within ExecUpdate() as e.g.
     * CONFLICT ... WHERE clause may prevent us from reaching that.
     *
     * This means we only ever continue when a new command in the current
     * transaction could see the row, even though in READ COMMITTED mode the
     * tuple will not be visible according to the current statement's
     * snapshot.  This is in line with the way UPDATE deals with newer tuple
     * versions.
     */
    ExecCheckTupleVisible(context->estate, relation, existing);
 
    /*
     * Make tuple and any needed join variables available to ExecQual and
     * ExecProject.  The EXCLUDED tuple is installed in ecxt_innertuple, while
     * the target's existing tuple is installed in the scantuple.  EXCLUDED
     * has been made to reference INNER_VAR in setrefs.c, but there is no
     * other redirection.
     */
    econtext->ecxt_scantuple = existing;
    econtext->ecxt_innertuple = excludedSlot;
    econtext->ecxt_outertuple = NULL;
 
    if (!ExecQual(onConflictSetWhere, econtext))
    {
        ExecClearTuple(existing);   /* see return below */
        InstrCountFiltered1(&mtstate->ps, 1);
        return true;            /* done with the tuple */
    }
 
    if (resultRelInfo->ri_WithCheckOptions != NIL)
    {
        /*
         * Check target's existing tuple against UPDATE-applicable USING
         * security barrier quals (if any), enforced here as RLS checks/WCOs.
         *
         * The rewriter creates UPDATE RLS checks/WCOs for UPDATE security
         * quals, and stores them as WCOs of "kind" WCO_RLS_CONFLICT_CHECK.
         * Since SELECT permission on the target table is always required for
         * INSERT ... ON CONFLICT DO UPDATE, the rewriter also adds SELECT RLS
         * checks/WCOs for SELECT security quals, using WCOs of the same kind,
         * and this check enforces them too.
         *
         * The rewriter will also have associated UPDATE-applicable straight
         * RLS checks/WCOs for the benefit of the ExecUpdate() call that
         * follows.  INSERTs and UPDATEs naturally have mutually exclusive WCO
         * kinds, so there is no danger of spurious over-enforcement in the
         * INSERT or UPDATE path.
         */
        ExecWithCheckOptions(WCO_RLS_CONFLICT_CHECK, resultRelInfo,
                             existing,
                             mtstate->ps.state);
    }
 
    /* Project the new tuple version */
    ExecProject(resultRelInfo->ri_onConflict->oc_ProjInfo);
 
    /*
     * Note that it is possible that the target tuple has been modified in
     * this session, after the above table_tuple_lock. We choose to not error
     * out in that case, in line with ExecUpdate's treatment of similar cases.
     * This can happen if an UPDATE is triggered from within ExecQual(),
     * ExecWithCheckOptions() or ExecProject() above, e.g. by selecting from a
     * wCTE in the ON CONFLICT's SET.
     */
 
    /* Execute UPDATE with projection */
    *returning = ExecUpdate(context, resultRelInfo,
                            conflictTid, NULL, existing,
                            resultRelInfo->ri_onConflict->oc_ProjSlot,
                            canSetTag);
 
    /*
     * Clear out existing tuple, as there might not be another conflict among
     * the next input rows. Don't want to hold resources till the end of the
     * query.  First though, make sure that the returning slot, if any, has a
     * local copy of any OLD pass-by-reference values, if it refers to any OLD
     * columns.
     */
    if (*returning != NULL &&
        resultRelInfo->ri_projectReturning->pi_state.flags & EEO_FLAG_HAS_OLD)
        ExecMaterializeSlot(*returning);
 
    ExecClearTuple(existing);
 
    return true;
}
 
/*
 * ExecOnConflictSelect --- execute SELECT of INSERT ON CONFLICT DO SELECT
 *
 * If SELECT FOR UPDATE/SHARE is specified, try to lock tuple as part of
 * speculative insertion.  If a qual originating from ON CONFLICT DO SELECT is
 * satisfied, select (but still lock row, even though it may not satisfy
 * estate's snapshot).
 *
 * Returns true if we're done (with or without a select), or false if the
 * caller must retry the INSERT from scratch.
 */
static bool
ExecOnConflictSelect(ModifyTableContext *context,
                     ResultRelInfo *resultRelInfo,
                     ItemPointer conflictTid,
                     TupleTableSlot *excludedSlot,
                     bool canSetTag,
                     TupleTableSlot **returning)
{
    ModifyTableState *mtstate = context->mtstate;
    ExprContext *econtext = mtstate->ps.ps_ExprContext;
    Relation    relation = resultRelInfo->ri_RelationDesc;
    ExprState  *onConflictSelectWhere = resultRelInfo->ri_onConflict->oc_WhereClause;
    TupleTableSlot *existing = resultRelInfo->ri_onConflict->oc_Existing;
    LockClauseStrength lockStrength = resultRelInfo->ri_onConflict->oc_LockStrength;
 
    /*
     * Parse analysis should have blocked ON CONFLICT for all system
     * relations, which includes these.  There's no fundamental obstacle to
     * supporting this; we'd just need to handle LOCKTAG_TUPLE appropriately.
     */
    Assert(!resultRelInfo->ri_needLockTagTuple);
 
    /* Fetch/lock existing tuple, according to the requested lock strength */
    if (lockStrength == LCS_NONE)
    {
        if (!table_tuple_fetch_row_version(relation,
                                           conflictTid,
                                           SnapshotAny,
                                           existing))
            elog(ERROR, "failed to fetch conflicting tuple for ON CONFLICT");
    }
    else
    {
        LockTupleMode lockmode;
 
        switch (lockStrength)
        {
            case LCS_FORKEYSHARE:
                lockmode = LockTupleKeyShare;
                break;
            case LCS_FORSHARE:
                lockmode = LockTupleShare;
                break;
            case LCS_FORNOKEYUPDATE:
                lockmode = LockTupleNoKeyExclusive;
                break;
            case LCS_FORUPDATE:
                lockmode = LockTupleExclusive;
                break;
            default:
                elog(ERROR, "Unexpected lock strength %d", (int) lockStrength);
        }
 
        if (!ExecOnConflictLockRow(context, existing, conflictTid,
                                   resultRelInfo->ri_RelationDesc, lockmode, false))
            return false;
    }
 
    /*
     * Verify that the tuple is visible to our MVCC snapshot if the current
     * isolation level mandates that.  See comments in ExecOnConflictUpdate().
     */
    ExecCheckTupleVisible(context->estate, relation, existing);
 
    /*
     * Make tuple and any needed join variables available to ExecQual.  The
     * EXCLUDED tuple is installed in ecxt_innertuple, while the target's
     * existing tuple is installed in the scantuple.  EXCLUDED has been made
     * to reference INNER_VAR in setrefs.c, but there is no other redirection.
     */
    econtext->ecxt_scantuple = existing;
    econtext->ecxt_innertuple = excludedSlot;
    econtext->ecxt_outertuple = NULL;
 
    if (!ExecQual(onConflictSelectWhere, econtext))
    {
        ExecClearTuple(existing);   /* see return below */
        InstrCountFiltered1(&mtstate->ps, 1);
        return true;            /* done with the tuple */
    }
 
    if (resultRelInfo->ri_WithCheckOptions != NIL)
    {
        /*
         * Check target's existing tuple against SELECT-applicable USING
         * security barrier quals (if any), enforced here as RLS checks/WCOs.
         *
         * The rewriter creates WCOs from the USING quals of SELECT policies,
         * and stores them as WCOs of "kind" WCO_RLS_CONFLICT_CHECK.  If FOR
         * UPDATE/SHARE was specified, UPDATE permissions are required on the
         * target table, and the rewriter also adds WCOs built from the USING
         * quals of UPDATE policies, using WCOs of the same kind, and this
         * check enforces them too.
         */
        ExecWithCheckOptions(WCO_RLS_CONFLICT_CHECK, resultRelInfo,
                             existing,
                             mtstate->ps.state);
    }
 
    /* RETURNING is required for DO SELECT */
    Assert(resultRelInfo->ri_projectReturning);
 
    *returning = ExecProcessReturning(context, resultRelInfo, false,
                                      existing, existing, context->planSlot);
 
    if (canSetTag)
        context->estate->es_processed++;
 
    /*
     * Before releasing the existing tuple, make sure that the returning slot
     * has a local copy of any pass-by-reference values.
     */
    ExecMaterializeSlot(*returning);
 
    /*
     * Clear out existing tuple, as there might not be another conflict among
     * the next input rows. Don't want to hold resources till the end of the
     * query.
     */
    ExecClearTuple(existing);
 
    return true;
}
 
/*
 * Perform MERGE.
 */
static TupleTableSlot *
ExecMerge(ModifyTableContext *context, ResultRelInfo *resultRelInfo,
          ItemPointer tupleid, HeapTuple oldtuple, bool canSetTag)
{
    TupleTableSlot *rslot = NULL;
    bool        matched;
 
    /*-----
     * If we are dealing with a WHEN MATCHED case, tupleid or oldtuple is
     * valid, depending on whether the result relation is a table or a view.
     * We execute the first action for which the additional WHEN MATCHED AND
     * quals pass.  If an action without quals is found, that action is
     * executed.
     *
     * Similarly, in the WHEN NOT MATCHED BY SOURCE case, tupleid or oldtuple
     * is valid, and we look at the given WHEN NOT MATCHED BY SOURCE actions
     * in sequence until one passes.  This is almost identical to the WHEN
     * MATCHED case, and both cases are handled by ExecMergeMatched().
     *
     * Finally, in the WHEN NOT MATCHED [BY TARGET] case, both tupleid and
     * oldtuple are invalid, and we look at the given WHEN NOT MATCHED [BY
     * TARGET] actions in sequence until one passes.
     *
     * Things get interesting in case of concurrent update/delete of the
     * target tuple. Such concurrent update/delete is detected while we are
     * executing a WHEN MATCHED or WHEN NOT MATCHED BY SOURCE action.
     *
     * A concurrent update can:
     *
     * 1. modify the target tuple so that the results from checking any
     *    additional quals attached to WHEN MATCHED or WHEN NOT MATCHED BY
     *    SOURCE actions potentially change, but the result from the join
     *    quals does not change.
     *
     *    In this case, we are still dealing with the same kind of match
     *    (MATCHED or NOT MATCHED BY SOURCE).  We recheck the same list of
     *    actions from the start and choose the first one that satisfies the
     *    new target tuple.
     *
     * 2. modify the target tuple in the WHEN MATCHED case so that the join
     *    quals no longer pass and hence the source and target tuples no
     *    longer match.
     *
     *    In this case, we are now dealing with a NOT MATCHED case, and we
     *    process both WHEN NOT MATCHED BY SOURCE and WHEN NOT MATCHED [BY
     *    TARGET] actions.  First ExecMergeMatched() processes the list of
     *    WHEN NOT MATCHED BY SOURCE actions in sequence until one passes,
     *    then ExecMergeNotMatched() processes any WHEN NOT MATCHED [BY
     *    TARGET] actions in sequence until one passes.  Thus we may execute
     *    two actions; one of each kind.
     *
     * Thus we support concurrent updates that turn MATCHED candidate rows
     * into NOT MATCHED rows.  However, we do not attempt to support cases
     * that would turn NOT MATCHED rows into MATCHED rows, or which would
     * cause a target row to match a different source row.
     *
     * A concurrent delete changes a WHEN MATCHED case to WHEN NOT MATCHED
     * [BY TARGET].
     *
     * ExecMergeMatched() takes care of following the update chain and
     * re-finding the qualifying WHEN MATCHED or WHEN NOT MATCHED BY SOURCE
     * action, as long as the target tuple still exists. If the target tuple
     * gets deleted or a concurrent update causes the join quals to fail, it
     * returns a matched status of false and we call ExecMergeNotMatched().
     * Given that ExecMergeMatched() always makes progress by following the
     * update chain and we never switch from ExecMergeNotMatched() to
     * ExecMergeMatched(), there is no risk of a livelock.
     */
    matched = tupleid != NULL || oldtuple != NULL;
    if (matched)
        rslot = ExecMergeMatched(context, resultRelInfo, tupleid, oldtuple,
                                 canSetTag, &matched);
 
    /*
     * Deal with the NOT MATCHED case (either a NOT MATCHED tuple from the
     * join, or a previously MATCHED tuple for which ExecMergeMatched() set
     * "matched" to false, indicating that it no longer matches).
     */
    if (!matched)
    {
        /*
         * If a concurrent update turned a MATCHED case into a NOT MATCHED
         * case, and we have both WHEN NOT MATCHED BY SOURCE and WHEN NOT
         * MATCHED [BY TARGET] actions, and there is a RETURNING clause,
         * ExecMergeMatched() may have already executed a WHEN NOT MATCHED BY
         * SOURCE action, and computed the row to return.  If so, we cannot
         * execute a WHEN NOT MATCHED [BY TARGET] action now, so mark it as
         * pending (to be processed on the next call to ExecModifyTable()).
         * Otherwise, just process the action now.
         */
        if (rslot == NULL)
            rslot = ExecMergeNotMatched(context, resultRelInfo, canSetTag);
        else
            context->mtstate->mt_merge_pending_not_matched = context->planSlot;
    }
 
    return rslot;
}
 
/*
 * Check and execute the first qualifying MATCHED or NOT MATCHED BY SOURCE
 * action, depending on whether the join quals are satisfied.  If the target
 * relation is a table, the current target tuple is identified by tupleid.
 * Otherwise, if the target relation is a view, oldtuple is the current target
 * tuple from the view.
 *
 * We start from the first WHEN MATCHED or WHEN NOT MATCHED BY SOURCE action
 * and check if the WHEN quals pass, if any. If the WHEN quals for the first
 * action do not pass, we check the second, then the third and so on. If we
 * reach the end without finding a qualifying action, we return NULL.
 * Otherwise, we execute the qualifying action and return its RETURNING
 * result, if any, or NULL.
 *
 * On entry, "*matched" is assumed to be true.  If a concurrent update or
 * delete is detected that causes the join quals to no longer pass, we set it
 * to false, indicating that the caller should process any NOT MATCHED [BY
 * TARGET] actions.
 *
 * After a concurrent update, we restart from the first action to look for a
 * new qualifying action to execute. If the join quals originally passed, and
 * the concurrent update caused them to no longer pass, then we switch from
 * the MATCHED to the NOT MATCHED BY SOURCE list of actions before restarting
 * (and setting "*matched" to false).  As a result we may execute a WHEN NOT
 * MATCHED BY SOURCE action, and set "*matched" to false, causing the caller
 * to also execute a WHEN NOT MATCHED [BY TARGET] action.
 */
static TupleTableSlot *
ExecMergeMatched(ModifyTableContext *context, ResultRelInfo *resultRelInfo,
                 ItemPointer tupleid, HeapTuple oldtuple, bool canSetTag,
                 bool *matched)
{
    ModifyTableState *mtstate = context->mtstate;
    List      **mergeActions = resultRelInfo->ri_MergeActions;
    ItemPointerData lockedtid;
    List       *actionStates;
    TupleTableSlot *newslot = NULL;
    TupleTableSlot *rslot = NULL;
    EState     *estate = context->estate;
    ExprContext *econtext = mtstate->ps.ps_ExprContext;
    bool        isNull;
    EPQState   *epqstate = &mtstate->mt_epqstate;
    ListCell   *l;
 
    /* Expect matched to be true on entry */
    Assert(*matched);
 
    /*
     * If there are no WHEN MATCHED or WHEN NOT MATCHED BY SOURCE actions, we
     * are done.
     */
    if (mergeActions[MERGE_WHEN_MATCHED] == NIL &&
        mergeActions[MERGE_WHEN_NOT_MATCHED_BY_SOURCE] == NIL)
        return NULL;
 
    /*
     * Make tuple and any needed join variables available to ExecQual and
     * ExecProject. The target's existing tuple is installed in the scantuple.
     * This target relation's slot is required only in the case of a MATCHED
     * or NOT MATCHED BY SOURCE tuple and UPDATE/DELETE actions.
     */
    econtext->ecxt_scantuple = resultRelInfo->ri_oldTupleSlot;
    econtext->ecxt_innertuple = context->planSlot;
    econtext->ecxt_outertuple = NULL;
 
    /*
     * This routine is only invoked for matched target rows, so we should
     * either have the tupleid of the target row, or an old tuple from the
     * target wholerow junk attr.
     */
    Assert(tupleid != NULL || oldtuple != NULL);
    ItemPointerSetInvalid(&lockedtid);
    if (oldtuple != NULL)
    {
        Assert(!resultRelInfo->ri_needLockTagTuple);
        ExecForceStoreHeapTuple(oldtuple, resultRelInfo->ri_oldTupleSlot,
                                false);
    }
    else
    {
        if (resultRelInfo->ri_needLockTagTuple)
        {
            /*
             * This locks even for CMD_DELETE, for CMD_NOTHING, and for tuples
             * that don't match mas_whenqual.  MERGE on system catalogs is a
             * minor use case, so don't bother optimizing those.
             */
            LockTuple(resultRelInfo->ri_RelationDesc, tupleid,
                      InplaceUpdateTupleLock);
            lockedtid = *tupleid;
        }
        if (!table_tuple_fetch_row_version(resultRelInfo->ri_RelationDesc,
                                           tupleid,
                                           SnapshotAny,
                                           resultRelInfo->ri_oldTupleSlot))
            elog(ERROR, "failed to fetch the target tuple");
    }
 
    /*
     * Test the join condition.  If it's satisfied, perform a MATCHED action.
     * Otherwise, perform a NOT MATCHED BY SOURCE action.
     *
     * Note that this join condition will be NULL if there are no NOT MATCHED
     * BY SOURCE actions --- see transform_MERGE_to_join().  In that case, we
     * need only consider MATCHED actions here.
     */
    if (ExecQual(resultRelInfo->ri_MergeJoinCondition, econtext))
        actionStates = mergeActions[MERGE_WHEN_MATCHED];
    else
        actionStates = mergeActions[MERGE_WHEN_NOT_MATCHED_BY_SOURCE];
 
lmerge_matched:
 
    foreach(l, actionStates)
    {
        MergeActionState *relaction = (MergeActionState *) lfirst(l);
        CmdType     commandType = relaction->mas_action->commandType;
        TM_Result   result;
        UpdateContext updateCxt = {0};
 
        /*
         * Test condition, if any.
         *
         * In the absence of any condition, we perform the action
         * unconditionally (no need to check separately since ExecQual() will
         * return true if there are no conditions to evaluate).
         */
        if (!ExecQual(relaction->mas_whenqual, econtext))
            continue;
 
        /*
         * Check if the existing target tuple meets the USING checks of
         * UPDATE/DELETE RLS policies. If those checks fail, we throw an
         * error.
         *
         * The WITH CHECK quals for UPDATE RLS policies are applied in
         * ExecUpdateAct() and hence we need not do anything special to handle
         * them.
         *
         * NOTE: We must do this after WHEN quals are evaluated, so that we
         * check policies only when they matter.
         */
        if (resultRelInfo->ri_WithCheckOptions && commandType != CMD_NOTHING)
        {
            ExecWithCheckOptions(commandType == CMD_UPDATE ?
                                 WCO_RLS_MERGE_UPDATE_CHECK : WCO_RLS_MERGE_DELETE_CHECK,
                                 resultRelInfo,
                                 resultRelInfo->ri_oldTupleSlot,
                                 context->mtstate->ps.state);
        }
 
        /* Perform stated action */
        switch (commandType)
        {
            case CMD_UPDATE:
 
                /*
                 * Project the output tuple, and use that to update the table.
                 * We don't need to filter out junk attributes, because the
                 * UPDATE action's targetlist doesn't have any.
                 */
                newslot = ExecProject(relaction->mas_proj);
 
                mtstate->mt_merge_action = relaction;
                if (!ExecUpdatePrologue(context, resultRelInfo,
                                        tupleid, NULL, newslot, &result))
                {
                    if (result == TM_Ok)
                        goto out;   /* "do nothing" */
 
                    break;      /* concurrent update/delete */
                }
 
                /* INSTEAD OF ROW UPDATE Triggers */
                if (resultRelInfo->ri_TrigDesc &&
                    resultRelInfo->ri_TrigDesc->trig_update_instead_row)
                {
                    if (!ExecIRUpdateTriggers(estate, resultRelInfo,
                                              oldtuple, newslot))
                        goto out;   /* "do nothing" */
                }
                else
                {
                    /* checked ri_needLockTagTuple above */
                    Assert(oldtuple == NULL);
 
                    result = ExecUpdateAct(context, resultRelInfo, tupleid,
                                           NULL, newslot, canSetTag,
                                           &updateCxt);
 
                    /*
                     * As in ExecUpdate(), if ExecUpdateAct() reports that a
                     * cross-partition update was done, then there's nothing
                     * else for us to do --- the UPDATE has been turned into a
                     * DELETE and an INSERT, and we must not perform any of
                     * the usual post-update tasks.  Also, the RETURNING tuple
                     * (if any) has been projected, so we can just return
                     * that.
                     */
                    if (updateCxt.crossPartUpdate)
                    {
                        mtstate->mt_merge_updated += 1;
                        rslot = context->cpUpdateReturningSlot;
                        goto out;
                    }
                }
 
                if (result == TM_Ok)
                {
                    ExecUpdateEpilogue(context, &updateCxt, resultRelInfo,
                                       tupleid, NULL, newslot);
                    mtstate->mt_merge_updated += 1;
                }
                break;
 
            case CMD_DELETE:
                mtstate->mt_merge_action = relaction;
                if (!ExecDeletePrologue(context, resultRelInfo, tupleid,
                                        NULL, NULL, &result))
                {
                    if (result == TM_Ok)
                        goto out;   /* "do nothing" */
 
                    break;      /* concurrent update/delete */
                }
 
                /* INSTEAD OF ROW DELETE Triggers */
                if (resultRelInfo->ri_TrigDesc &&
                    resultRelInfo->ri_TrigDesc->trig_delete_instead_row)
                {
                    if (!ExecIRDeleteTriggers(estate, resultRelInfo,
                                              oldtuple))
                        goto out;   /* "do nothing" */
                }
                else
                {
                    /* checked ri_needLockTagTuple above */
                    Assert(oldtuple == NULL);
 
                    result = ExecDeleteAct(context, resultRelInfo, tupleid,
                                           false);
                }
 
                if (result == TM_Ok)
                {
                    ExecDeleteEpilogue(context, resultRelInfo, tupleid, NULL,
                                       false);
                    mtstate->mt_merge_deleted += 1;
                }
                break;
 
            case CMD_NOTHING:
                /* Doing nothing is always OK */
                result = TM_Ok;
                break;
 
            default:
                elog(ERROR, "unknown action in MERGE WHEN clause");
        }
 
        switch (result)
        {
            case TM_Ok:
                /* all good; perform final actions */
                if (canSetTag && commandType != CMD_NOTHING)
                    (estate->es_processed)++;
 
                break;
 
            case TM_SelfModified:
 
                /*
                 * The target tuple was already updated or deleted by the
                 * current command, or by a later command in the current
                 * transaction.  The former case is explicitly disallowed by
                 * the SQL standard for MERGE, which insists that the MERGE
                 * join condition should not join a target row to more than
                 * one source row.
                 *
                 * The latter case arises if the tuple is modified by a
                 * command in a BEFORE trigger, or perhaps by a command in a
                 * volatile function used in the query.  In such situations we
                 * should not ignore the MERGE action, but it is equally
                 * unsafe to proceed.  We don't want to discard the original
                 * MERGE action while keeping the triggered actions based on
                 * it; and it would be no better to allow the original MERGE
                 * action while discarding the updates that it triggered.  So
                 * throwing an error is the only safe course.
                 */
                if (context->tmfd.cmax != estate->es_output_cid)
                    ereport(ERROR,
                            (errcode(ERRCODE_TRIGGERED_DATA_CHANGE_VIOLATION),
                             errmsg("tuple to be updated or deleted was already modified by an operation triggered by the current command"),
                             errhint("Consider using an AFTER trigger instead of a BEFORE trigger to propagate changes to other rows.")));
 
                if (TransactionIdIsCurrentTransactionId(context->tmfd.xmax))
                    ereport(ERROR,
                            (errcode(ERRCODE_CARDINALITY_VIOLATION),
                    /* translator: %s is a SQL command name */
                             errmsg("%s command cannot affect row a second time",
                                    "MERGE"),
                             errhint("Ensure that not more than one source row matches any one target row.")));
 
                /* This shouldn't happen */
                elog(ERROR, "attempted to update or delete invisible tuple");
                break;
 
            case TM_Deleted:
                if (IsolationUsesXactSnapshot())
                    ereport(ERROR,
                            (errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
                             errmsg("could not serialize access due to concurrent delete")));
 
                /*
                 * If the tuple was already deleted, set matched to false to
                 * let caller handle it under NOT MATCHED [BY TARGET] clauses.
                 */
                *matched = false;
                goto out;
 
            case TM_Updated:
                {
                    bool        was_matched;
                    Relation    resultRelationDesc;
                    TupleTableSlot *epqslot,
                               *inputslot;
                    LockTupleMode lockmode;
 
                    if (IsolationUsesXactSnapshot())
                        ereport(ERROR,
                                (errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
                                 errmsg("could not serialize access due to concurrent update")));
 
                    /*
                     * The target tuple was concurrently updated by some other
                     * transaction.  If we are currently processing a MATCHED
                     * action, use EvalPlanQual() with the new version of the
                     * tuple and recheck the join qual, to detect a change
                     * from the MATCHED to the NOT MATCHED cases.  If we are
                     * already processing a NOT MATCHED BY SOURCE action, we
                     * skip this (cannot switch from NOT MATCHED BY SOURCE to
                     * MATCHED).
                     */
                    was_matched = relaction->mas_action->matchKind == MERGE_WHEN_MATCHED;
                    resultRelationDesc = resultRelInfo->ri_RelationDesc;
                    lockmode = ExecUpdateLockMode(estate, resultRelInfo);
 
                    if (was_matched)
                        inputslot = EvalPlanQualSlot(epqstate, resultRelationDesc,
                                                     resultRelInfo->ri_RangeTableIndex);
                    else
                        inputslot = resultRelInfo->ri_oldTupleSlot;
 
                    result = table_tuple_lock(resultRelationDesc, tupleid,
                                              estate->es_snapshot,
                                              inputslot, estate->es_output_cid,
                                              lockmode, LockWaitBlock,
                                              TUPLE_LOCK_FLAG_FIND_LAST_VERSION,
                                              &context->tmfd);
                    switch (result)
                    {
                        case TM_Ok:
 
                            /*
                             * If the tuple was updated and migrated to
                             * another partition concurrently, the current
                             * MERGE implementation can't follow.  There's
                             * probably a better way to handle this case, but
                             * it'd require recognizing the relation to which
                             * the tuple moved, and setting our current
                             * resultRelInfo to that.
                             */
                            if (ItemPointerIndicatesMovedPartitions(tupleid))
                                ereport(ERROR,
                                        (errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
                                         errmsg("tuple to be merged was already moved to another partition due to concurrent update")));
 
                            /*
                             * If this was a MATCHED case, use EvalPlanQual()
                             * to recheck the join condition.
                             */
                            if (was_matched)
                            {
                                epqslot = EvalPlanQual(epqstate,
                                                       resultRelationDesc,
                                                       resultRelInfo->ri_RangeTableIndex,
                                                       inputslot);
 
                                /*
                                 * If the subplan didn't return a tuple, then
                                 * we must be dealing with an inner join for
                                 * which the join condition no longer matches.
                                 * This can only happen if there are no NOT
                                 * MATCHED actions, and so there is nothing
                                 * more to do.
                                 */
                                if (TupIsNull(epqslot))
                                    goto out;
 
                                /*
                                 * If we got a NULL ctid from the subplan, the
                                 * join quals no longer pass and we switch to
                                 * the NOT MATCHED BY SOURCE case.
                                 */
                                (void) ExecGetJunkAttribute(epqslot,
                                                            resultRelInfo->ri_RowIdAttNo,
                                                            &isNull);
                                if (isNull)
                                    *matched = false;
 
                                /*
                                 * Otherwise, recheck the join quals to see if
                                 * we need to switch to the NOT MATCHED BY
                                 * SOURCE case.
                                 */
                                if (resultRelInfo->ri_needLockTagTuple)
                                {
                                    if (ItemPointerIsValid(&lockedtid))
                                        UnlockTuple(resultRelInfo->ri_RelationDesc, &lockedtid,
                                                    InplaceUpdateTupleLock);
                                    LockTuple(resultRelInfo->ri_RelationDesc, tupleid,
                                              InplaceUpdateTupleLock);
                                    lockedtid = *tupleid;
                                }
 
                                if (!table_tuple_fetch_row_version(resultRelationDesc,
                                                                   tupleid,
                                                                   SnapshotAny,
                                                                   resultRelInfo->ri_oldTupleSlot))
                                    elog(ERROR, "failed to fetch the target tuple");
 
                                if (*matched)
                                    *matched = ExecQual(resultRelInfo->ri_MergeJoinCondition,
                                                        econtext);
 
                                /* Switch lists, if necessary */
                                if (!*matched)
                                {
                                    actionStates = mergeActions[MERGE_WHEN_NOT_MATCHED_BY_SOURCE];
 
                                    /*
                                     * If we have both NOT MATCHED BY SOURCE
                                     * and NOT MATCHED BY TARGET actions (a
                                     * full join between the source and target
                                     * relations), the single previously
                                     * matched tuple from the outer plan node
                                     * is treated as two not matched tuples,
                                     * in the same way as if they had not
                                     * matched to start with.  Therefore, we
                                     * must adjust the outer plan node's tuple
                                     * count, if we're instrumenting the
                                     * query, to get the correct "skipped" row
                                     * count --- see show_modifytable_info().
                                     */
                                    if (outerPlanState(mtstate)->instrument &&
                                        mergeActions[MERGE_WHEN_NOT_MATCHED_BY_SOURCE] &&
                                        mergeActions[MERGE_WHEN_NOT_MATCHED_BY_TARGET])
                                        InstrUpdateTupleCount(outerPlanState(mtstate)->instrument, 1.0);
                                }
                            }
 
                            /*
                             * Loop back and process the MATCHED or NOT
                             * MATCHED BY SOURCE actions from the start.
                             */
                            goto lmerge_matched;
 
                        case TM_Deleted:
 
                            /*
                             * tuple already deleted; tell caller to run NOT
                             * MATCHED [BY TARGET] actions
                             */
                            *matched = false;
                            goto out;
 
                        case TM_SelfModified:
 
                            /*
                             * This can be reached when following an update
                             * chain from a tuple updated by another session,
                             * reaching a tuple that was already updated or
                             * deleted by the current command, or by a later
                             * command in the current transaction. As above,
                             * this should always be treated as an error.
                             */
                            if (context->tmfd.cmax != estate->es_output_cid)
                                ereport(ERROR,
                                        (errcode(ERRCODE_TRIGGERED_DATA_CHANGE_VIOLATION),
                                         errmsg("tuple to be updated or deleted was already modified by an operation triggered by the current command"),
                                         errhint("Consider using an AFTER trigger instead of a BEFORE trigger to propagate changes to other rows.")));
 
                            if (TransactionIdIsCurrentTransactionId(context->tmfd.xmax))
                                ereport(ERROR,
                                        (errcode(ERRCODE_CARDINALITY_VIOLATION),
                                /* translator: %s is a SQL command name */
                                         errmsg("%s command cannot affect row a second time",
                                                "MERGE"),
                                         errhint("Ensure that not more than one source row matches any one target row.")));
 
                            /* This shouldn't happen */
                            elog(ERROR, "attempted to update or delete invisible tuple");
                            goto out;
 
                        default:
                            /* see table_tuple_lock call in ExecDelete() */
                            elog(ERROR, "unexpected table_tuple_lock status: %u",
                                 result);
                            goto out;
                    }
                }
 
            case TM_Invisible:
            case TM_WouldBlock:
            case TM_BeingModified:
                /* these should not occur */
                elog(ERROR, "unexpected tuple operation result: %d", result);
                break;
        }
 
        /* Process RETURNING if present */
        if (resultRelInfo->ri_projectReturning)
        {
            switch (commandType)
            {
                case CMD_UPDATE:
                    rslot = ExecProcessReturning(context,
                                                 resultRelInfo,
                                                 false,
                                                 resultRelInfo->ri_oldTupleSlot,
                                                 newslot,
                                                 context->planSlot);
                    break;
 
                case CMD_DELETE:
                    rslot = ExecProcessReturning(context,
                                                 resultRelInfo,
                                                 true,
                                                 resultRelInfo->ri_oldTupleSlot,
                                                 NULL,
                                                 context->planSlot);
                    break;
 
                case CMD_NOTHING:
                    break;
 
                default:
                    elog(ERROR, "unrecognized commandType: %d",
                         (int) commandType);
            }
        }
 
        /*
         * We've activated one of the WHEN clauses, so we don't search
         * further. This is required behaviour, not an optimization.
         */
        break;
    }
 
    /*
     * Successfully executed an action or no qualifying action was found.
     */
out:
    if (ItemPointerIsValid(&lockedtid))
        UnlockTuple(resultRelInfo->ri_RelationDesc, &lockedtid,
                    InplaceUpdateTupleLock);
    return rslot;
}
 
/*
 * Execute the first qualifying NOT MATCHED [BY TARGET] action.
 */
static TupleTableSlot *
ExecMergeNotMatched(ModifyTableContext *context, ResultRelInfo *resultRelInfo,
                    bool canSetTag)
{
    ModifyTableState *mtstate = context->mtstate;
    ExprContext *econtext = mtstate->ps.ps_ExprContext;
    List       *actionStates;
    TupleTableSlot *rslot = NULL;
    ListCell   *l;
 
    /*
     * For INSERT actions, the root relation's merge action is OK since the
     * INSERT's targetlist and the WHEN conditions can only refer to the
     * source relation and hence it does not matter which result relation we
     * work with.
     *
     * XXX does this mean that we can avoid creating copies of actionStates on
     * partitioned tables, for not-matched actions?
     */
    actionStates = resultRelInfo->ri_MergeActions[MERGE_WHEN_NOT_MATCHED_BY_TARGET];
 
    /*
     * Make source tuple available to ExecQual and ExecProject. We don't need
     * the target tuple, since the WHEN quals and targetlist can't refer to
     * the target columns.
     */
    econtext->ecxt_scantuple = NULL;
    econtext->ecxt_innertuple = context->planSlot;
    econtext->ecxt_outertuple = NULL;
 
    foreach(l, actionStates)
    {
        MergeActionState *action = (MergeActionState *) lfirst(l);
        CmdType     commandType = action->mas_action->commandType;
        TupleTableSlot *newslot;
 
        /*
         * Test condition, if any.
         *
         * In the absence of any condition, we perform the action
         * unconditionally (no need to check separately since ExecQual() will
         * return true if there are no conditions to evaluate).
         */
        if (!ExecQual(action->mas_whenqual, econtext))
            continue;
 
        /* Perform stated action */
        switch (commandType)
        {
            case CMD_INSERT:
 
                /*
                 * Project the tuple.  In case of a partitioned table, the
                 * projection was already built to use the root's descriptor,
                 * so we don't need to map the tuple here.
                 */
                newslot = ExecProject(action->mas_proj);
                mtstate->mt_merge_action = action;
 
                rslot = ExecInsert(context, mtstate->rootResultRelInfo,
                                   newslot, canSetTag, NULL, NULL);
                mtstate->mt_merge_inserted += 1;
                break;
            case CMD_NOTHING:
                /* Do nothing */
                break;
            default:
                elog(ERROR, "unknown action in MERGE WHEN NOT MATCHED clause");
        }
 
        /*
         * We've activated one of the WHEN clauses, so we don't search
         * further. This is required behaviour, not an optimization.
         */
        break;
    }
 
    return rslot;
}
 
/*
 * Initialize state for execution of MERGE.
 */
void
ExecInitMerge(ModifyTableState *mtstate, EState *estate)
{
    List       *mergeActionLists = mtstate->mt_mergeActionLists;
    List       *mergeJoinConditions = mtstate->mt_mergeJoinConditions;
    ResultRelInfo *rootRelInfo = mtstate->rootResultRelInfo;
    ResultRelInfo *resultRelInfo;
    ExprContext *econtext;
    ListCell   *lc;
    int         i;
 
    if (mergeActionLists == NIL)
        return;
 
    mtstate->mt_merge_subcommands = 0;
 
    if (mtstate->ps.ps_ExprContext == NULL)
        ExecAssignExprContext(estate, &mtstate->ps);
    econtext = mtstate->ps.ps_ExprContext;
 
    /*
     * Create a MergeActionState for each action on the mergeActionList and
     * add it to either a list of matched actions or not-matched actions.
     *
     * Similar logic appears in ExecInitPartitionInfo(), so if changing
     * anything here, do so there too.
     */
    i = 0;
    foreach(lc, mergeActionLists)
    {
        List       *mergeActionList = lfirst(lc);
        Node       *joinCondition;
        TupleDesc   relationDesc;
        ListCell   *l;
 
        joinCondition = (Node *) list_nth(mergeJoinConditions, i);
        resultRelInfo = mtstate->resultRelInfo + i;
        i++;
        relationDesc = RelationGetDescr(resultRelInfo->ri_RelationDesc);
 
        /* initialize slots for MERGE fetches from this rel */
        if (unlikely(!resultRelInfo->ri_projectNewInfoValid))
            ExecInitMergeTupleSlots(mtstate, resultRelInfo);
 
        /* initialize state for join condition checking */
        resultRelInfo->ri_MergeJoinCondition =
            ExecInitQual((List *) joinCondition, &mtstate->ps);
 
        foreach(l, mergeActionList)
        {
            MergeAction *action = (MergeAction *) lfirst(l);
            MergeActionState *action_state;
            TupleTableSlot *tgtslot;
            TupleDesc   tgtdesc;
 
            /*
             * Build action merge state for this rel.  (For partitions,
             * equivalent code exists in ExecInitPartitionInfo.)
             */
            action_state = makeNode(MergeActionState);
            action_state->mas_action = action;
            action_state->mas_whenqual = ExecInitQual((List *) action->qual,
                                                      &mtstate->ps);
 
            /*
             * We create three lists - one for each MergeMatchKind - and stick
             * the MergeActionState into the appropriate list.
             */
            resultRelInfo->ri_MergeActions[action->matchKind] =
                lappend(resultRelInfo->ri_MergeActions[action->matchKind],
                        action_state);
 
            switch (action->commandType)
            {
                case CMD_INSERT:
                    /* INSERT actions always use rootRelInfo */
                    ExecCheckPlanOutput(rootRelInfo->ri_RelationDesc,
                                        action->targetList);
 
                    /*
                     * If the MERGE targets a partitioned table, any INSERT
                     * actions must be routed through it, not the child
                     * relations. Initialize the routing struct and the root
                     * table's "new" tuple slot for that, if not already done.
                     * The projection we prepare, for all relations, uses the
                     * root relation descriptor, and targets the plan's root
                     * slot.  (This is consistent with the fact that we
                     * checked the plan output to match the root relation,
                     * above.)
                     */
                    if (rootRelInfo->ri_RelationDesc->rd_rel->relkind ==
                        RELKIND_PARTITIONED_TABLE)
                    {
                        if (mtstate->mt_partition_tuple_routing == NULL)
                        {
                            /*
                             * Initialize planstate for routing if not already
                             * done.
                             *
                             * Note that the slot is managed as a standalone
                             * slot belonging to ModifyTableState, so we pass
                             * NULL for the 2nd argument.
                             */
                            mtstate->mt_root_tuple_slot =
                                table_slot_create(rootRelInfo->ri_RelationDesc,
                                                  NULL);
                            mtstate->mt_partition_tuple_routing =
                                ExecSetupPartitionTupleRouting(estate,
                                                               rootRelInfo->ri_RelationDesc);
                        }
                        tgtslot = mtstate->mt_root_tuple_slot;
                        tgtdesc = RelationGetDescr(rootRelInfo->ri_RelationDesc);
                    }
                    else
                    {
                        /*
                         * If the MERGE targets an inherited table, we insert
                         * into the root table, so we must initialize its
                         * "new" tuple slot, if not already done, and use its
                         * relation descriptor for the projection.
                         *
                         * For non-inherited tables, rootRelInfo and
                         * resultRelInfo are the same, and the "new" tuple
                         * slot will already have been initialized.
                         */
                        if (rootRelInfo->ri_newTupleSlot == NULL)
                            rootRelInfo->ri_newTupleSlot =
                                table_slot_create(rootRelInfo->ri_RelationDesc,
                                                  &estate->es_tupleTable);
 
                        tgtslot = rootRelInfo->ri_newTupleSlot;
                        tgtdesc = RelationGetDescr(rootRelInfo->ri_RelationDesc);
                    }
 
                    action_state->mas_proj =
                        ExecBuildProjectionInfo(action->targetList, econtext,
                                                tgtslot,
                                                &mtstate->ps,
                                                tgtdesc);
 
                    mtstate->mt_merge_subcommands |= MERGE_INSERT;
                    break;
                case CMD_UPDATE:
                    action_state->mas_proj =
                        ExecBuildUpdateProjection(action->targetList,
                                                  true,
                                                  action->updateColnos,
                                                  relationDesc,
                                                  econtext,
                                                  resultRelInfo->ri_newTupleSlot,
                                                  &mtstate->ps);
                    mtstate->mt_merge_subcommands |= MERGE_UPDATE;
                    break;
                case CMD_DELETE:
                    mtstate->mt_merge_subcommands |= MERGE_DELETE;
                    break;
                case CMD_NOTHING:
                    break;
                default:
                    elog(ERROR, "unknown action in MERGE WHEN clause");
                    break;
            }
        }
    }
 
    /*
     * If the MERGE targets an inherited table, any INSERT actions will use
     * rootRelInfo, and rootRelInfo will not be in the resultRelInfo array.
     * Therefore we must initialize its WITH CHECK OPTION constraints and
     * RETURNING projection, as ExecInitModifyTable did for the resultRelInfo
     * entries.
     *
     * Note that the planner does not build a withCheckOptionList or
     * returningList for the root relation, but as in ExecInitPartitionInfo,
     * we can use the first resultRelInfo entry as a reference to calculate
     * the attno's for the root table.
     */
    if (rootRelInfo != mtstate->resultRelInfo &&
        rootRelInfo->ri_RelationDesc->rd_rel->relkind != RELKIND_PARTITIONED_TABLE &&
        (mtstate->mt_merge_subcommands & MERGE_INSERT) != 0)
    {
        ModifyTable *node = (ModifyTable *) mtstate->ps.plan;
        Relation    rootRelation = rootRelInfo->ri_RelationDesc;
        Relation    firstResultRel = mtstate->resultRelInfo[0].ri_RelationDesc;
        int         firstVarno = mtstate->resultRelInfo[0].ri_RangeTableIndex;
        AttrMap    *part_attmap = NULL;
        bool        found_whole_row;
 
        if (node->withCheckOptionLists != NIL)
        {
            List       *wcoList;
            List       *wcoExprs = NIL;
 
            /* There should be as many WCO lists as result rels */
            Assert(list_length(node->withCheckOptionLists) ==
                   list_length(node->resultRelations));
 
            /*
             * Use the first WCO list as a reference. In the most common case,
             * this will be for the same relation as rootRelInfo, and so there
             * will be no need to adjust its attno's.
             */
            wcoList = linitial(node->withCheckOptionLists);
            if (rootRelation != firstResultRel)
            {
                /* Convert any Vars in it to contain the root's attno's */
                part_attmap =
                    build_attrmap_by_name(RelationGetDescr(rootRelation),
                                          RelationGetDescr(firstResultRel),
                                          false);
 
                wcoList = (List *)
                    map_variable_attnos((Node *) wcoList,
                                        firstVarno, 0,
                                        part_attmap,
                                        RelationGetForm(rootRelation)->reltype,
                                        &found_whole_row);
            }
 
            foreach(lc, wcoList)
            {
                WithCheckOption *wco = lfirst_node(WithCheckOption, lc);
                ExprState  *wcoExpr = ExecInitQual(castNode(List, wco->qual),
                                                   &mtstate->ps);
 
                wcoExprs = lappend(wcoExprs, wcoExpr);
            }
 
            rootRelInfo->ri_WithCheckOptions = wcoList;
            rootRelInfo->ri_WithCheckOptionExprs = wcoExprs;
        }
 
        if (node->returningLists != NIL)
        {
            List       *returningList;
 
            /* There should be as many returning lists as result rels */
            Assert(list_length(node->returningLists) ==
                   list_length(node->resultRelations));
 
            /*
             * Use the first returning list as a reference. In the most common
             * case, this will be for the same relation as rootRelInfo, and so
             * there will be no need to adjust its attno's.
             */
            returningList = linitial(node->returningLists);
            if (rootRelation != firstResultRel)
            {
                /* Convert any Vars in it to contain the root's attno's */
                if (part_attmap == NULL)
                    part_attmap =
                        build_attrmap_by_name(RelationGetDescr(rootRelation),
                                              RelationGetDescr(firstResultRel),
                                              false);
 
                returningList = (List *)
                    map_variable_attnos((Node *) returningList,
                                        firstVarno, 0,
                                        part_attmap,
                                        RelationGetForm(rootRelation)->reltype,
                                        &found_whole_row);
            }
            rootRelInfo->ri_returningList = returningList;
 
            /* Initialize the RETURNING projection */
            rootRelInfo->ri_projectReturning =
                ExecBuildProjectionInfo(returningList, econtext,
                                        mtstate->ps.ps_ResultTupleSlot,
                                        &mtstate->ps,
                                        RelationGetDescr(rootRelation));
        }
    }
}
 
/*
 * Initializes the tuple slots in a ResultRelInfo for any MERGE action.
 *
 * We mark 'projectNewInfoValid' even though the projections themselves
 * are not initialized here.
 */
void
ExecInitMergeTupleSlots(ModifyTableState *mtstate,
                        ResultRelInfo *resultRelInfo)
{
    EState     *estate = mtstate->ps.state;
 
    Assert(!resultRelInfo->ri_projectNewInfoValid);
 
    resultRelInfo->ri_oldTupleSlot =
        table_slot_create(resultRelInfo->ri_RelationDesc,
                          &estate->es_tupleTable);
    resultRelInfo->ri_newTupleSlot =
        table_slot_create(resultRelInfo->ri_RelationDesc,
                          &estate->es_tupleTable);
    resultRelInfo->ri_projectNewInfoValid = true;
}
 
/*
 * Process BEFORE EACH STATEMENT triggers
 */
static void
fireBSTriggers(ModifyTableState *node)
{
    ModifyTable *plan = (ModifyTable *) node->ps.plan;
    ResultRelInfo *resultRelInfo = node->rootResultRelInfo;
 
    switch (node->operation)
    {
        case CMD_INSERT:
            ExecBSInsertTriggers(node->ps.state, resultRelInfo);
            if (plan->onConflictAction == ONCONFLICT_UPDATE)
                ExecBSUpdateTriggers(node->ps.state,
                                     resultRelInfo);
            break;
        case CMD_UPDATE:
            ExecBSUpdateTriggers(node->ps.state, resultRelInfo);
            break;
        case CMD_DELETE:
            ExecBSDeleteTriggers(node->ps.state, resultRelInfo);
            break;
        case CMD_MERGE:
            if (node->mt_merge_subcommands & MERGE_INSERT)
                ExecBSInsertTriggers(node->ps.state, resultRelInfo);
            if (node->mt_merge_subcommands & MERGE_UPDATE)
                ExecBSUpdateTriggers(node->ps.state, resultRelInfo);
            if (node->mt_merge_subcommands & MERGE_DELETE)
                ExecBSDeleteTriggers(node->ps.state, resultRelInfo);
            break;
        default:
            elog(ERROR, "unknown operation");
            break;
    }
}
 
/*
 * Process AFTER EACH STATEMENT triggers
 */
static void
fireASTriggers(ModifyTableState *node)
{
    ModifyTable *plan = (ModifyTable *) node->ps.plan;
    ResultRelInfo *resultRelInfo = node->rootResultRelInfo;
 
    switch (node->operation)
    {
        case CMD_INSERT:
            if (plan->onConflictAction == ONCONFLICT_UPDATE)
                ExecASUpdateTriggers(node->ps.state,
                                     resultRelInfo,
                                     node->mt_oc_transition_capture);
            ExecASInsertTriggers(node->ps.state, resultRelInfo,
                                 node->mt_transition_capture);
            break;
        case CMD_UPDATE:
            ExecASUpdateTriggers(node->ps.state, resultRelInfo,
                                 node->mt_transition_capture);
            break;
        case CMD_DELETE:
            ExecASDeleteTriggers(node->ps.state, resultRelInfo,
                                 node->mt_transition_capture);
            break;
        case CMD_MERGE:
            if (node->mt_merge_subcommands & MERGE_DELETE)
                ExecASDeleteTriggers(node->ps.state, resultRelInfo,
                                     node->mt_transition_capture);
            if (node->mt_merge_subcommands & MERGE_UPDATE)
                ExecASUpdateTriggers(node->ps.state, resultRelInfo,
                                     node->mt_transition_capture);
            if (node->mt_merge_subcommands & MERGE_INSERT)
                ExecASInsertTriggers(node->ps.state, resultRelInfo,
                                     node->mt_transition_capture);
            break;
        default:
            elog(ERROR, "unknown operation");
            break;
    }
}
 
/*
 * Set up the state needed for collecting transition tuples for AFTER
 * triggers.
 */
static void
ExecSetupTransitionCaptureState(ModifyTableState *mtstate, EState *estate)
{
    ModifyTable *plan = (ModifyTable *) mtstate->ps.plan;
    ResultRelInfo *targetRelInfo = mtstate->rootResultRelInfo;
 
    /* Check for transition tables on the directly targeted relation. */
    mtstate->mt_transition_capture =
        MakeTransitionCaptureState(targetRelInfo->ri_TrigDesc,
                                   RelationGetRelid(targetRelInfo->ri_RelationDesc),
                                   mtstate->operation);
    if (plan->operation == CMD_INSERT &&
        plan->onConflictAction == ONCONFLICT_UPDATE)
        mtstate->mt_oc_transition_capture =
            MakeTransitionCaptureState(targetRelInfo->ri_TrigDesc,
                                       RelationGetRelid(targetRelInfo->ri_RelationDesc),
                                       CMD_UPDATE);
}
 
/*
 * ExecPrepareTupleRouting --- prepare for routing one tuple
 *
 * Determine the partition in which the tuple in slot is to be inserted,
 * and return its ResultRelInfo in *partRelInfo.  The return value is
 * a slot holding the tuple of the partition rowtype.
 *
 * This also sets the transition table information in mtstate based on the
 * selected partition.
 */
static TupleTableSlot *
ExecPrepareTupleRouting(ModifyTableState *mtstate,
                        EState *estate,
                        PartitionTupleRouting *proute,
                        ResultRelInfo *targetRelInfo,
                        TupleTableSlot *slot,
                        ResultRelInfo **partRelInfo)
{
    ResultRelInfo *partrel;
    TupleConversionMap *map;
 
    /*
     * Lookup the target partition's ResultRelInfo.  If ExecFindPartition does
     * not find a valid partition for the tuple in 'slot' then an error is
     * raised.  An error may also be raised if the found partition is not a
     * valid target for INSERTs.  This is required since a partitioned table
     * UPDATE to another partition becomes a DELETE+INSERT.
     */
    partrel = ExecFindPartition(mtstate, targetRelInfo, proute, slot, estate);
 
    /*
     * If we're capturing transition tuples, we might need to convert from the
     * partition rowtype to root partitioned table's rowtype.  But if there
     * are no BEFORE triggers on the partition that could change the tuple, we
     * can just remember the original unconverted tuple to avoid a needless
     * round trip conversion.
     */
    if (mtstate->mt_transition_capture != NULL)
    {
        bool        has_before_insert_row_trig;
 
        has_before_insert_row_trig = (partrel->ri_TrigDesc &&
                                      partrel->ri_TrigDesc->trig_insert_before_row);
 
        mtstate->mt_transition_capture->tcs_original_insert_tuple =
            !has_before_insert_row_trig ? slot : NULL;
    }
 
    /*
     * Convert the tuple, if necessary.
     */
    map = ExecGetRootToChildMap(partrel, estate);
    if (map != NULL)
    {
        TupleTableSlot *new_slot = partrel->ri_PartitionTupleSlot;
 
        slot = execute_attr_map_slot(map->attrMap, slot, new_slot);
    }
 
    *partRelInfo = partrel;
    return slot;
}
 
/* ----------------------------------------------------------------
 *     ExecModifyTable
 *
 *      Perform table modifications as required, and return RETURNING results
 *      if needed.
 * ----------------------------------------------------------------
 */
static TupleTableSlot *
ExecModifyTable(PlanState *pstate)
{
    ModifyTableState *node = castNode(ModifyTableState, pstate);
    ModifyTableContext context;
    EState     *estate = node->ps.state;
    CmdType     operation = node->operation;
    ResultRelInfo *resultRelInfo;
    PlanState  *subplanstate;
    TupleTableSlot *slot;
    TupleTableSlot *oldSlot;
    ItemPointerData tuple_ctid;
    HeapTupleData oldtupdata;
    HeapTuple   oldtuple;
    ItemPointer tupleid;
    bool        tuplock;
 
    CHECK_FOR_INTERRUPTS();
 
    /*
     * This should NOT get called during EvalPlanQual; we should have passed a
     * subplan tree to EvalPlanQual, instead.  Use a runtime test not just
     * Assert because this condition is easy to miss in testing.  (Note:
     * although ModifyTable should not get executed within an EvalPlanQual
     * operation, we do have to allow it to be initialized and shut down in
     * case it is within a CTE subplan.  Hence this test must be here, not in
     * ExecInitModifyTable.)
     */
    if (estate->es_epq_active != NULL)
        elog(ERROR, "ModifyTable should not be called during EvalPlanQual");
 
    /*
     * If we've already completed processing, don't try to do more.  We need
     * this test because ExecPostprocessPlan might call us an extra time, and
     * our subplan's nodes aren't necessarily robust against being called
     * extra times.
     */
    if (node->mt_done)
        return NULL;
 
    /*
     * On first call, fire BEFORE STATEMENT triggers before proceeding.
     */
    if (node->fireBSTriggers)
    {
        fireBSTriggers(node);
        node->fireBSTriggers = false;
    }
 
    /* Preload local variables */
    resultRelInfo = node->resultRelInfo + node->mt_lastResultIndex;
    subplanstate = outerPlanState(node);
 
    /* Set global context */
    context.mtstate = node;
    context.epqstate = &node->mt_epqstate;
    context.estate = estate;
 
    /*
     * Fetch rows from subplan, and execute the required table modification
     * for each row.
     */
    for (;;)
    {
        /*
         * Reset the per-output-tuple exprcontext.  This is needed because
         * triggers expect to use that context as workspace.  It's a bit ugly
         * to do this below the top level of the plan, however.  We might need
         * to rethink this later.
         */
        ResetPerTupleExprContext(estate);
 
        /*
         * Reset per-tuple memory context used for processing on conflict and
         * returning clauses, to free any expression evaluation storage
         * allocated in the previous cycle.
         */
        if (pstate->ps_ExprContext)
            ResetExprContext(pstate->ps_ExprContext);
 
        /*
         * If there is a pending MERGE ... WHEN NOT MATCHED [BY TARGET] action
         * to execute, do so now --- see the comments in ExecMerge().
         */
        if (node->mt_merge_pending_not_matched != NULL)
        {
            context.planSlot = node->mt_merge_pending_not_matched;
            context.cpDeletedSlot = NULL;
 
            slot = ExecMergeNotMatched(&context, node->resultRelInfo,
                                       node->canSetTag);
 
            /* Clear the pending action */
            node->mt_merge_pending_not_matched = NULL;
 
            /*
             * If we got a RETURNING result, return it to the caller.  We'll
             * continue the work on next call.
             */
            if (slot)
                return slot;
 
            continue;           /* continue with the next tuple */
        }
 
        /* Fetch the next row from subplan */
        context.planSlot = ExecProcNode(subplanstate);
        context.cpDeletedSlot = NULL;
 
        /* No more tuples to process? */
        if (TupIsNull(context.planSlot))
            break;
 
        /*
         * When there are multiple result relations, each tuple contains a
         * junk column that gives the OID of the rel from which it came.
         * Extract it and select the correct result relation.
         */
        if (AttributeNumberIsValid(node->mt_resultOidAttno))
        {
            Datum       datum;
            bool        isNull;
            Oid         resultoid;
 
            datum = ExecGetJunkAttribute(context.planSlot, node->mt_resultOidAttno,
                                         &isNull);
            if (isNull)
            {
                /*
                 * For commands other than MERGE, any tuples having InvalidOid
                 * for tableoid are errors.  For MERGE, we may need to handle
                 * them as WHEN NOT MATCHED clauses if any, so do that.
                 *
                 * Note that we use the node's toplevel resultRelInfo, not any
                 * specific partition's.
                 */
                if (operation == CMD_MERGE)
                {
                    EvalPlanQualSetSlot(&node->mt_epqstate, context.planSlot);
 
                    slot = ExecMerge(&context, node->resultRelInfo,
                                     NULL, NULL, node->canSetTag);
 
                    /*
                     * If we got a RETURNING result, return it to the caller.
                     * We'll continue the work on next call.
                     */
                    if (slot)
                        return slot;
 
                    continue;   /* continue with the next tuple */
                }
 
                elog(ERROR, "tableoid is NULL");
            }
            resultoid = DatumGetObjectId(datum);
 
            /* If it's not the same as last time, we need to locate the rel */
            if (resultoid != node->mt_lastResultOid)
                resultRelInfo = ExecLookupResultRelByOid(node, resultoid,
                                                         false, true);
        }
 
        /*
         * If resultRelInfo->ri_usesFdwDirectModify is true, all we need to do
         * here is compute the RETURNING expressions.
         */
        if (resultRelInfo->ri_usesFdwDirectModify)
        {
            Assert(resultRelInfo->ri_projectReturning);
 
            /*
             * A scan slot containing the data that was actually inserted,
             * updated or deleted has already been made available to
             * ExecProcessReturning by IterateDirectModify, so no need to
             * provide it here.  The individual old and new slots are not
             * needed, since direct-modify is disabled if the RETURNING list
             * refers to OLD/NEW values.
             */
            Assert((resultRelInfo->ri_projectReturning->pi_state.flags & EEO_FLAG_HAS_OLD) == 0 &&
                   (resultRelInfo->ri_projectReturning->pi_state.flags & EEO_FLAG_HAS_NEW) == 0);
 
            slot = ExecProcessReturning(&context, resultRelInfo,
                                        operation == CMD_DELETE,
                                        NULL, NULL, context.planSlot);
 
            return slot;
        }
 
        EvalPlanQualSetSlot(&node->mt_epqstate, context.planSlot);
        slot = context.planSlot;
 
        tupleid = NULL;
        oldtuple = NULL;
 
        /*
         * For UPDATE/DELETE/MERGE, fetch the row identity info for the tuple
         * to be updated/deleted/merged.  For a heap relation, that's a TID;
         * otherwise we may have a wholerow junk attr that carries the old
         * tuple in toto.  Keep this in step with the part of
         * ExecInitModifyTable that sets up ri_RowIdAttNo.
         */
        if (operation == CMD_UPDATE || operation == CMD_DELETE ||
            operation == CMD_MERGE)
        {
            char        relkind;
            Datum       datum;
            bool        isNull;
 
            relkind = resultRelInfo->ri_RelationDesc->rd_rel->relkind;
            if (relkind == RELKIND_RELATION ||
                relkind == RELKIND_MATVIEW ||
                relkind == RELKIND_PARTITIONED_TABLE)
            {
                /*
                 * ri_RowIdAttNo refers to a ctid attribute.  See the comment
                 * in ExecInitModifyTable().
                 */
                Assert(AttributeNumberIsValid(resultRelInfo->ri_RowIdAttNo) ||
                       relkind == RELKIND_PARTITIONED_TABLE);
                datum = ExecGetJunkAttribute(slot,
                                             resultRelInfo->ri_RowIdAttNo,
                                             &isNull);
 
                /*
                 * For commands other than MERGE, any tuples having a null row
                 * identifier are errors.  For MERGE, we may need to handle
                 * them as WHEN NOT MATCHED clauses if any, so do that.
                 *
                 * Note that we use the node's toplevel resultRelInfo, not any
                 * specific partition's.
                 */
                if (isNull)
                {
                    if (operation == CMD_MERGE)
                    {
                        EvalPlanQualSetSlot(&node->mt_epqstate, context.planSlot);
 
                        slot = ExecMerge(&context, node->resultRelInfo,
                                         NULL, NULL, node->canSetTag);
 
                        /*
                         * If we got a RETURNING result, return it to the
                         * caller.  We'll continue the work on next call.
                         */
                        if (slot)
                            return slot;
 
                        continue;   /* continue with the next tuple */
                    }
 
                    elog(ERROR, "ctid is NULL");
                }
 
                tupleid = (ItemPointer) DatumGetPointer(datum);
                tuple_ctid = *tupleid;  /* be sure we don't free ctid!! */
                tupleid = &tuple_ctid;
            }
 
            /*
             * Use the wholerow attribute, when available, to reconstruct the
             * old relation tuple.  The old tuple serves one or both of two
             * purposes: 1) it serves as the OLD tuple for row triggers, 2) it
             * provides values for any unchanged columns for the NEW tuple of
             * an UPDATE, because the subplan does not produce all the columns
             * of the target table.
             *
             * Note that the wholerow attribute does not carry system columns,
             * so foreign table triggers miss seeing those, except that we
             * know enough here to set t_tableOid.  Quite separately from
             * this, the FDW may fetch its own junk attrs to identify the row.
             *
             * Other relevant relkinds, currently limited to views, always
             * have a wholerow attribute.
             */
            else if (AttributeNumberIsValid(resultRelInfo->ri_RowIdAttNo))
            {
                datum = ExecGetJunkAttribute(slot,
                                             resultRelInfo->ri_RowIdAttNo,
                                             &isNull);
 
                /*
                 * For commands other than MERGE, any tuples having a null row
                 * identifier are errors.  For MERGE, we may need to handle
                 * them as WHEN NOT MATCHED clauses if any, so do that.
                 *
                 * Note that we use the node's toplevel resultRelInfo, not any
                 * specific partition's.
                 */
                if (isNull)
                {
                    if (operation == CMD_MERGE)
                    {
                        EvalPlanQualSetSlot(&node->mt_epqstate, context.planSlot);
 
                        slot = ExecMerge(&context, node->resultRelInfo,
                                         NULL, NULL, node->canSetTag);
 
                        /*
                         * If we got a RETURNING result, return it to the
                         * caller.  We'll continue the work on next call.
                         */
                        if (slot)
                            return slot;
 
                        continue;   /* continue with the next tuple */
                    }
 
                    elog(ERROR, "wholerow is NULL");
                }
 
                oldtupdata.t_data = DatumGetHeapTupleHeader(datum);
                oldtupdata.t_len =
                    HeapTupleHeaderGetDatumLength(oldtupdata.t_data);
                ItemPointerSetInvalid(&(oldtupdata.t_self));
                /* Historically, view triggers see invalid t_tableOid. */
                oldtupdata.t_tableOid =
                    (relkind == RELKIND_VIEW) ? InvalidOid :
                    RelationGetRelid(resultRelInfo->ri_RelationDesc);
 
                oldtuple = &oldtupdata;
            }
            else
            {
                /* Only foreign tables are allowed to omit a row-ID attr */
                Assert(relkind == RELKIND_FOREIGN_TABLE);
            }
        }
 
        switch (operation)
        {
            case CMD_INSERT:
                /* Initialize projection info if first time for this table */
                if (unlikely(!resultRelInfo->ri_projectNewInfoValid))
                    ExecInitInsertProjection(node, resultRelInfo);
                slot = ExecGetInsertNewTuple(resultRelInfo, context.planSlot);
                slot = ExecInsert(&context, resultRelInfo, slot,
                                  node->canSetTag, NULL, NULL);
                break;
 
            case CMD_UPDATE:
                tuplock = false;
 
                /* Initialize projection info if first time for this table */
                if (unlikely(!resultRelInfo->ri_projectNewInfoValid))
                    ExecInitUpdateProjection(node, resultRelInfo);
 
                /*
                 * Make the new tuple by combining plan's output tuple with
                 * the old tuple being updated.
                 */
                oldSlot = resultRelInfo->ri_oldTupleSlot;
                if (oldtuple != NULL)
                {
                    Assert(!resultRelInfo->ri_needLockTagTuple);
                    /* Use the wholerow junk attr as the old tuple. */
                    ExecForceStoreHeapTuple(oldtuple, oldSlot, false);
                }
                else
                {
                    /* Fetch the most recent version of old tuple. */
                    Relation    relation = resultRelInfo->ri_RelationDesc;
 
                    if (resultRelInfo->ri_needLockTagTuple)
                    {
                        LockTuple(relation, tupleid, InplaceUpdateTupleLock);
                        tuplock = true;
                    }
                    if (!table_tuple_fetch_row_version(relation, tupleid,
                                                       SnapshotAny,
                                                       oldSlot))
                        elog(ERROR, "failed to fetch tuple being updated");
                }
                slot = ExecGetUpdateNewTuple(resultRelInfo, context.planSlot,
                                             oldSlot);
 
                /* Now apply the update. */
                slot = ExecUpdate(&context, resultRelInfo, tupleid, oldtuple,
                                  oldSlot, slot, node->canSetTag);
                if (tuplock)
                    UnlockTuple(resultRelInfo->ri_RelationDesc, tupleid,
                                InplaceUpdateTupleLock);
                break;
 
            case CMD_DELETE:
                slot = ExecDelete(&context, resultRelInfo, tupleid, oldtuple,
                                  true, false, node->canSetTag, NULL, NULL, NULL);
                break;
 
            case CMD_MERGE:
                slot = ExecMerge(&context, resultRelInfo, tupleid, oldtuple,
                                 node->canSetTag);
                break;
 
            default:
                elog(ERROR, "unknown operation");
                break;
        }
 
        /*
         * If we got a RETURNING result, return it to caller.  We'll continue
         * the work on next call.
         */
        if (slot)
            return slot;
    }
 
    /*
     * Insert remaining tuples for batch insert.
     */
    if (estate->es_insert_pending_result_relations != NIL)
        ExecPendingInserts(estate);
 
    /*
     * We're done, but fire AFTER STATEMENT triggers before exiting.
     */
    fireASTriggers(node);
 
    node->mt_done = true;
 
    return NULL;
}
 
/*
 * ExecLookupResultRelByOid
 *      If the table with given OID is among the result relations to be
 *      updated by the given ModifyTable node, return its ResultRelInfo.
 *
 * If not found, return NULL if missing_ok, else raise error.
 *
 * If update_cache is true, then upon successful lookup, update the node's
 * one-element cache.  ONLY ExecModifyTable may pass true for this.
 */
ResultRelInfo *
ExecLookupResultRelByOid(ModifyTableState *node, Oid resultoid,
                         bool missing_ok, bool update_cache)
{
    if (node->mt_resultOidHash)
    {
        /* Use the pre-built hash table to locate the rel */
        MTTargetRelLookup *mtlookup;
 
        mtlookup = (MTTargetRelLookup *)
            hash_search(node->mt_resultOidHash, &resultoid, HASH_FIND, NULL);
        if (mtlookup)
        {
            if (update_cache)
            {
                node->mt_lastResultOid = resultoid;
                node->mt_lastResultIndex = mtlookup->relationIndex;
            }
            return node->resultRelInfo + mtlookup->relationIndex;
        }
    }
    else
    {
        /* With few target rels, just search the ResultRelInfo array */
        for (int ndx = 0; ndx < node->mt_nrels; ndx++)
        {
            ResultRelInfo *rInfo = node->resultRelInfo + ndx;
 
            if (RelationGetRelid(rInfo->ri_RelationDesc) == resultoid)
            {
                if (update_cache)
                {
                    node->mt_lastResultOid = resultoid;
                    node->mt_lastResultIndex = ndx;
                }
                return rInfo;
            }
        }
    }
 
    if (!missing_ok)
        elog(ERROR, "incorrect result relation OID %u", resultoid);
    return NULL;
}
 
/* ----------------------------------------------------------------
 *      ExecInitModifyTable
 * ----------------------------------------------------------------
 */
ModifyTableState *
ExecInitModifyTable(ModifyTable *node, EState *estate, int eflags)
{
    ModifyTableState *mtstate;
    Plan       *subplan = outerPlan(node);
    CmdType     operation = node->operation;
    int         total_nrels = list_length(node->resultRelations);
    int         nrels;
    List       *resultRelations = NIL;
    List       *withCheckOptionLists = NIL;
    List       *returningLists = NIL;
    List       *updateColnosLists = NIL;
    List       *mergeActionLists = NIL;
    List       *mergeJoinConditions = NIL;
    ResultRelInfo *resultRelInfo;
    List       *arowmarks;
    ListCell   *l;
    int         i;
    Relation    rel;
 
    /* check for unsupported flags */
    Assert(!(eflags & (EXEC_FLAG_BACKWARD | EXEC_FLAG_MARK)));
 
    /*
     * Only consider unpruned relations for initializing their ResultRelInfo
     * struct and other fields such as withCheckOptions, etc.
     *
     * Note: We must avoid pruning every result relation.  This is important
     * for MERGE, since even if every result relation is pruned from the
     * subplan, there might still be NOT MATCHED rows, for which there may be
     * INSERT actions to perform.  To allow these actions to be found, at
     * least one result relation must be kept.  Also, when inserting into a
     * partitioned table, ExecInitPartitionInfo() needs a ResultRelInfo struct
     * as a reference for building the ResultRelInfo of the target partition.
     * In either case, it doesn't matter which result relation is kept, so we
     * just keep the first one, if all others have been pruned.  See also,
     * ExecDoInitialPruning(), which ensures that this first result relation
     * has been locked.
     */
    i = 0;
    foreach(l, node->resultRelations)
    {
        Index       rti = lfirst_int(l);
        bool        keep_rel;
 
        keep_rel = bms_is_member(rti, estate->es_unpruned_relids);
        if (!keep_rel && i == total_nrels - 1 && resultRelations == NIL)
        {
            /* all result relations pruned; keep the first one */
            keep_rel = true;
            rti = linitial_int(node->resultRelations);
            i = 0;
        }
 
        if (keep_rel)
        {
            resultRelations = lappend_int(resultRelations, rti);
            if (node->withCheckOptionLists)
            {
                List       *withCheckOptions = list_nth_node(List,
                                                             node->withCheckOptionLists,
                                                             i);
 
                withCheckOptionLists = lappend(withCheckOptionLists, withCheckOptions);
            }
            if (node->returningLists)
            {
                List       *returningList = list_nth_node(List,
                                                          node->returningLists,
                                                          i);
 
                returningLists = lappend(returningLists, returningList);
            }
            if (node->updateColnosLists)
            {
                List       *updateColnosList = list_nth(node->updateColnosLists, i);
 
                updateColnosLists = lappend(updateColnosLists, updateColnosList);
            }
            if (node->mergeActionLists)
            {
                List       *mergeActionList = list_nth(node->mergeActionLists, i);
 
                mergeActionLists = lappend(mergeActionLists, mergeActionList);
            }
            if (node->mergeJoinConditions)
            {
                List       *mergeJoinCondition = list_nth(node->mergeJoinConditions, i);
 
                mergeJoinConditions = lappend(mergeJoinConditions, mergeJoinCondition);
            }
        }
        i++;
    }
    nrels = list_length(resultRelations);
    Assert(nrels > 0);
 
    /*
     * create state structure
     */
    mtstate = makeNode(ModifyTableState);
    mtstate->ps.plan = (Plan *) node;
    mtstate->ps.state = estate;
    mtstate->ps.ExecProcNode = ExecModifyTable;
 
    mtstate->operation = operation;
    mtstate->canSetTag = node->canSetTag;
    mtstate->mt_done = false;
 
    mtstate->mt_nrels = nrels;
    mtstate->resultRelInfo = palloc_array(ResultRelInfo, nrels);
 
    mtstate->mt_merge_pending_not_matched = NULL;
    mtstate->mt_merge_inserted = 0;
    mtstate->mt_merge_updated = 0;
    mtstate->mt_merge_deleted = 0;
    mtstate->mt_updateColnosLists = updateColnosLists;
    mtstate->mt_mergeActionLists = mergeActionLists;
    mtstate->mt_mergeJoinConditions = mergeJoinConditions;
 
    /*----------
     * Resolve the target relation. This is the same as:
     *
     * - the relation for which we will fire FOR STATEMENT triggers,
     * - the relation into whose tuple format all captured transition tuples
     *   must be converted, and
     * - the root partitioned table used for tuple routing.
     *
     * If it's a partitioned or inherited table, the root partition or
     * appendrel RTE doesn't appear elsewhere in the plan and its RT index is
     * given explicitly in node->rootRelation.  Otherwise, the target relation
     * is the sole relation in the node->resultRelations list and, since it can
     * never be pruned, also in the resultRelations list constructed above.
     *----------
     */
    if (node->rootRelation > 0)
    {
        Assert(bms_is_member(node->rootRelation, estate->es_unpruned_relids));
        mtstate->rootResultRelInfo = makeNode(ResultRelInfo);
        ExecInitResultRelation(estate, mtstate->rootResultRelInfo,
                               node->rootRelation);
    }
    else
    {
        Assert(list_length(node->resultRelations) == 1);
        Assert(list_length(resultRelations) == 1);
        mtstate->rootResultRelInfo = mtstate->resultRelInfo;
        ExecInitResultRelation(estate, mtstate->resultRelInfo,
                               linitial_int(resultRelations));
    }
 
    /* set up epqstate with dummy subplan data for the moment */
    EvalPlanQualInit(&mtstate->mt_epqstate, estate, NULL, NIL,
                     node->epqParam, resultRelations);
    mtstate->fireBSTriggers = true;
 
    /*
     * Build state for collecting transition tuples.  This requires having a
     * valid trigger query context, so skip it in explain-only mode.
     */
    if (!(eflags & EXEC_FLAG_EXPLAIN_ONLY))
        ExecSetupTransitionCaptureState(mtstate, estate);
 
    /*
     * Open all the result relations and initialize the ResultRelInfo structs.
     * (But root relation was initialized above, if it's part of the array.)
     * We must do this before initializing the subplan, because direct-modify
     * FDWs expect their ResultRelInfos to be available.
     */
    resultRelInfo = mtstate->resultRelInfo;
    i = 0;
    foreach(l, resultRelations)
    {
        Index       resultRelation = lfirst_int(l);
        List       *mergeActions = NIL;
 
        if (mergeActionLists)
            mergeActions = list_nth(mergeActionLists, i);
 
        if (resultRelInfo != mtstate->rootResultRelInfo)
        {
            ExecInitResultRelation(estate, resultRelInfo, resultRelation);
 
            /*
             * For child result relations, store the root result relation
             * pointer.  We do so for the convenience of places that want to
             * look at the query's original target relation but don't have the
             * mtstate handy.
             */
            resultRelInfo->ri_RootResultRelInfo = mtstate->rootResultRelInfo;
        }
 
        /* Initialize the usesFdwDirectModify flag */
        resultRelInfo->ri_usesFdwDirectModify =
            bms_is_member(i, node->fdwDirectModifyPlans);
 
        /*
         * Verify result relation is a valid target for the current operation
         */
        CheckValidResultRel(resultRelInfo, operation, node->onConflictAction,
                            mergeActions);
 
        resultRelInfo++;
        i++;
    }
 
    /*
     * Now we may initialize the subplan.
     */
    outerPlanState(mtstate) = ExecInitNode(subplan, estate, eflags);
 
    /*
     * Do additional per-result-relation initialization.
     */
    for (i = 0; i < nrels; i++)
    {
        resultRelInfo = &mtstate->resultRelInfo[i];
 
        /* Let FDWs init themselves for foreign-table result rels */
        if (!resultRelInfo->ri_usesFdwDirectModify &&
            resultRelInfo->ri_FdwRoutine != NULL &&
            resultRelInfo->ri_FdwRoutine->BeginForeignModify != NULL)
        {
            List       *fdw_private = (List *) list_nth(node->fdwPrivLists, i);
 
            resultRelInfo->ri_FdwRoutine->BeginForeignModify(mtstate,
                                                             resultRelInfo,
                                                             fdw_private,
                                                             i,
                                                             eflags);
        }
 
        /*
         * For UPDATE/DELETE/MERGE, find the appropriate junk attr now, either
         * a 'ctid' or 'wholerow' attribute depending on relkind.  For foreign
         * tables, the FDW might have created additional junk attr(s), but
         * those are no concern of ours.
         */
        if (operation == CMD_UPDATE || operation == CMD_DELETE ||
            operation == CMD_MERGE)
        {
            char        relkind;
 
            relkind = resultRelInfo->ri_RelationDesc->rd_rel->relkind;
            if (relkind == RELKIND_RELATION ||
                relkind == RELKIND_MATVIEW ||
                relkind == RELKIND_PARTITIONED_TABLE)
            {
                resultRelInfo->ri_RowIdAttNo =
                    ExecFindJunkAttributeInTlist(subplan->targetlist, "ctid");
 
                /*
                 * For heap relations, a ctid junk attribute must be present.
                 * Partitioned tables should only appear here when all leaf
                 * partitions were pruned, in which case no rows can be
                 * produced and ctid is not needed.
                 */
                if (relkind == RELKIND_PARTITIONED_TABLE)
                    Assert(nrels == 1);
                else if (!AttributeNumberIsValid(resultRelInfo->ri_RowIdAttNo))
                    elog(ERROR, "could not find junk ctid column");
            }
            else if (relkind == RELKIND_FOREIGN_TABLE)
            {
                /*
                 * We don't support MERGE with foreign tables for now.  (It's
                 * problematic because the implementation uses CTID.)
                 */
                Assert(operation != CMD_MERGE);
 
                /*
                 * When there is a row-level trigger, there should be a
                 * wholerow attribute.  We also require it to be present in
                 * UPDATE and MERGE, so we can get the values of unchanged
                 * columns.
                 */
                resultRelInfo->ri_RowIdAttNo =
                    ExecFindJunkAttributeInTlist(subplan->targetlist,
                                                 "wholerow");
                if ((mtstate->operation == CMD_UPDATE || mtstate->operation == CMD_MERGE) &&
                    !AttributeNumberIsValid(resultRelInfo->ri_RowIdAttNo))
                    elog(ERROR, "could not find junk wholerow column");
            }
            else
            {
                /* Other valid target relkinds must provide wholerow */
                resultRelInfo->ri_RowIdAttNo =
                    ExecFindJunkAttributeInTlist(subplan->targetlist,
                                                 "wholerow");
                if (!AttributeNumberIsValid(resultRelInfo->ri_RowIdAttNo))
                    elog(ERROR, "could not find junk wholerow column");
            }
        }
    }
 
    /*
     * If this is an inherited update/delete/merge, there will be a junk
     * attribute named "tableoid" present in the subplan's targetlist.  It
     * will be used to identify the result relation for a given tuple to be
     * updated/deleted/merged.
     */
    mtstate->mt_resultOidAttno =
        ExecFindJunkAttributeInTlist(subplan->targetlist, "tableoid");
    Assert(AttributeNumberIsValid(mtstate->mt_resultOidAttno) || total_nrels == 1);
    mtstate->mt_lastResultOid = InvalidOid; /* force lookup at first tuple */
    mtstate->mt_lastResultIndex = 0;    /* must be zero if no such attr */
 
    /* Get the root target relation */
    rel = mtstate->rootResultRelInfo->ri_RelationDesc;
 
    /*
     * Build state for tuple routing if it's a partitioned INSERT.  An UPDATE
     * or MERGE might need this too, but only if it actually moves tuples
     * between partitions; in that case setup is done by
     * ExecCrossPartitionUpdate.
     */
    if (rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE &&
        operation == CMD_INSERT)
        mtstate->mt_partition_tuple_routing =
            ExecSetupPartitionTupleRouting(estate, rel);
 
    /*
     * Initialize any WITH CHECK OPTION constraints if needed.
     */
    resultRelInfo = mtstate->resultRelInfo;
    foreach(l, withCheckOptionLists)
    {
        List       *wcoList = (List *) lfirst(l);
        List       *wcoExprs = NIL;
        ListCell   *ll;
 
        foreach(ll, wcoList)
        {
            WithCheckOption *wco = (WithCheckOption *) lfirst(ll);
            ExprState  *wcoExpr = ExecInitQual((List *) wco->qual,
                                               &mtstate->ps);
 
            wcoExprs = lappend(wcoExprs, wcoExpr);
        }
 
        resultRelInfo->ri_WithCheckOptions = wcoList;
        resultRelInfo->ri_WithCheckOptionExprs = wcoExprs;
        resultRelInfo++;
    }
 
    /*
     * Initialize RETURNING projections if needed.
     */
    if (returningLists)
    {
        TupleTableSlot *slot;
        ExprContext *econtext;
 
        /*
         * Initialize result tuple slot and assign its rowtype using the plan
         * node's declared targetlist, which the planner set up to be the same
         * as the first (before runtime pruning) RETURNING list.  We assume
         * all the result rels will produce compatible output.
         */
        ExecInitResultTupleSlotTL(&mtstate->ps, &TTSOpsVirtual);
        slot = mtstate->ps.ps_ResultTupleSlot;
 
        /* Need an econtext too */
        if (mtstate->ps.ps_ExprContext == NULL)
            ExecAssignExprContext(estate, &mtstate->ps);
        econtext = mtstate->ps.ps_ExprContext;
 
        /*
         * Build a projection for each result rel.
         */
        resultRelInfo = mtstate->resultRelInfo;
        foreach(l, returningLists)
        {
            List       *rlist = (List *) lfirst(l);
 
            resultRelInfo->ri_returningList = rlist;
            resultRelInfo->ri_projectReturning =
                ExecBuildProjectionInfo(rlist, econtext, slot, &mtstate->ps,
                                        resultRelInfo->ri_RelationDesc->rd_att);
            resultRelInfo++;
        }
    }
    else
    {
        /*
         * We still must construct a dummy result tuple type, because InitPlan
         * expects one (maybe should change that?).
         */
        ExecInitResultTypeTL(&mtstate->ps);
 
        mtstate->ps.ps_ExprContext = NULL;
    }
 
    /* Set the list of arbiter indexes if needed for ON CONFLICT */
    resultRelInfo = mtstate->resultRelInfo;
    if (node->onConflictAction != ONCONFLICT_NONE)
    {
        /* insert may only have one relation, inheritance is not expanded */
        Assert(total_nrels == 1);
        resultRelInfo->ri_onConflictArbiterIndexes = node->arbiterIndexes;
    }
 
    /*
     * For ON CONFLICT DO SELECT/UPDATE, initialize the ON CONFLICT action
     * state.
     */
    if (node->onConflictAction == ONCONFLICT_UPDATE ||
        node->onConflictAction == ONCONFLICT_SELECT)
    {
        OnConflictActionState *onconfl = makeNode(OnConflictActionState);
 
        /* already exists if created by RETURNING processing above */
        if (mtstate->ps.ps_ExprContext == NULL)
            ExecAssignExprContext(estate, &mtstate->ps);
 
        /* action state for DO SELECT/UPDATE */
        resultRelInfo->ri_onConflict = onconfl;
 
        /* lock strength for DO SELECT [FOR UPDATE/SHARE] */
        onconfl->oc_LockStrength = node->onConflictLockStrength;
 
        /* initialize slot for the existing tuple */
        onconfl->oc_Existing =
            table_slot_create(resultRelInfo->ri_RelationDesc,
                              &mtstate->ps.state->es_tupleTable);
 
        /*
         * For ON CONFLICT DO UPDATE, initialize target list and projection.
         */
        if (node->onConflictAction == ONCONFLICT_UPDATE)
        {
            ExprContext *econtext;
            TupleDesc   relationDesc;
 
            econtext = mtstate->ps.ps_ExprContext;
            relationDesc = resultRelInfo->ri_RelationDesc->rd_att;
 
            /*
             * Create the tuple slot for the UPDATE SET projection. We want a
             * slot of the table's type here, because the slot will be used to
             * insert into the table, and for RETURNING processing - which may
             * access system attributes.
             */
            onconfl->oc_ProjSlot =
                table_slot_create(resultRelInfo->ri_RelationDesc,
                                  &mtstate->ps.state->es_tupleTable);
 
            /* build UPDATE SET projection state */
            onconfl->oc_ProjInfo =
                ExecBuildUpdateProjection(node->onConflictSet,
                                          true,
                                          node->onConflictCols,
                                          relationDesc,
                                          econtext,
                                          onconfl->oc_ProjSlot,
                                          &mtstate->ps);
        }
 
        /* initialize state to evaluate the WHERE clause, if any */
        if (node->onConflictWhere)
        {
            ExprState  *qualexpr;
 
            qualexpr = ExecInitQual((List *) node->onConflictWhere,
                                    &mtstate->ps);
            onconfl->oc_WhereClause = qualexpr;
        }
    }
 
    /*
     * If needed, initialize the target range for FOR PORTION OF.
     */
    if (node->forPortionOf)
    {
        ResultRelInfo *rootRelInfo;
        TupleDesc   tupDesc;
        ForPortionOfExpr *forPortionOf;
        Datum       targetRange;
        bool        isNull;
        ExprContext *econtext;
        ExprState  *exprState;
        ForPortionOfState *fpoState;
 
        rootRelInfo = mtstate->resultRelInfo;
        if (rootRelInfo->ri_RootResultRelInfo)
            rootRelInfo = rootRelInfo->ri_RootResultRelInfo;
 
        tupDesc = rootRelInfo->ri_RelationDesc->rd_att;
        forPortionOf = (ForPortionOfExpr *) node->forPortionOf;
 
        /* Eval the FOR PORTION OF target */
        if (mtstate->ps.ps_ExprContext == NULL)
            ExecAssignExprContext(estate, &mtstate->ps);
        econtext = mtstate->ps.ps_ExprContext;
 
        exprState = ExecPrepareExpr((Expr *) forPortionOf->targetRange, estate);
        targetRange = ExecEvalExpr(exprState, econtext, &isNull);
 
        /*
         * FOR PORTION OF ... TO ... FROM should never give us a NULL target,
         * but FOR PORTION OF (...) could.
         */
        if (isNull)
            ereport(ERROR,
                    (errmsg("FOR PORTION OF target was null")),
                    executor_errposition(estate, forPortionOf->targetLocation));
 
        /* Create state for FOR PORTION OF operation */
 
        fpoState = makeNode(ForPortionOfState);
        fpoState->fp_rangeName = forPortionOf->range_name;
        fpoState->fp_rangeType = forPortionOf->rangeType;
        fpoState->fp_rangeAttno = forPortionOf->rangeVar->varattno;
        fpoState->fp_targetRange = targetRange;
 
        /* Initialize slot for the existing tuple */
 
        fpoState->fp_Existing =
            table_slot_create(rootRelInfo->ri_RelationDesc,
                              &mtstate->ps.state->es_tupleTable);
 
        /* Create the tuple slot for INSERTing the temporal leftovers */
 
        fpoState->fp_Leftover =
            ExecInitExtraTupleSlot(mtstate->ps.state, tupDesc, &TTSOpsVirtual);
 
        rootRelInfo->ri_forPortionOf = fpoState;
 
        /*
         * Make sure the root relation has the FOR PORTION OF clause too. Each
         * partition needs its own TupleTableSlot, since they can have
         * different descriptors, so they'll use the root fpoState to
         * initialize one if necessary.
         */
        if (node->rootRelation > 0)
            mtstate->rootResultRelInfo->ri_forPortionOf = fpoState;
 
        if (rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE &&
            mtstate->mt_partition_tuple_routing == NULL)
        {
            /*
             * We will need tuple routing to insert temporal leftovers. Since
             * we are initializing things before ExecCrossPartitionUpdate
             * runs, we must do everything it needs as well.
             */
            Relation    rootRel = mtstate->rootResultRelInfo->ri_RelationDesc;
            MemoryContext oldcxt;
 
            /* Things built here have to last for the query duration. */
            oldcxt = MemoryContextSwitchTo(estate->es_query_cxt);
 
            mtstate->mt_partition_tuple_routing =
                ExecSetupPartitionTupleRouting(estate, rootRel);
 
            /*
             * Before a partition's tuple can be re-routed, it must first be
             * converted to the root's format, so we'll need a slot for
             * storing such tuples.
             */
            Assert(mtstate->mt_root_tuple_slot == NULL);
            mtstate->mt_root_tuple_slot = table_slot_create(rootRel, NULL);
 
            MemoryContextSwitchTo(oldcxt);
        }
 
        /*
         * Don't free the ExprContext here because the result must last for
         * the whole query.
         */
    }
 
    /*
     * If we have any secondary relations in an UPDATE or DELETE, they need to
     * be treated like non-locked relations in SELECT FOR UPDATE, i.e., the
     * EvalPlanQual mechanism needs to be told about them.  This also goes for
     * the source relations in a MERGE.  Locate the relevant ExecRowMarks.
     */
    arowmarks = NIL;
    foreach(l, node->rowMarks)
    {
        PlanRowMark *rc = lfirst_node(PlanRowMark, l);
        RangeTblEntry *rte = exec_rt_fetch(rc->rti, estate);
        ExecRowMark *erm;
        ExecAuxRowMark *aerm;
 
        /* ignore "parent" rowmarks; they are irrelevant at runtime */
        if (rc->isParent)
            continue;
 
        /*
         * Also ignore rowmarks belonging to child tables that have been
         * pruned in ExecDoInitialPruning().
         */
        if (rte->rtekind == RTE_RELATION &&
            !bms_is_member(rc->rti, estate->es_unpruned_relids))
            continue;
 
        /* Find ExecRowMark and build ExecAuxRowMark */
        erm = ExecFindRowMark(estate, rc->rti, false);
        aerm = ExecBuildAuxRowMark(erm, subplan->targetlist);
        arowmarks = lappend(arowmarks, aerm);
    }
 
    /* For a MERGE command, initialize its state */
    if (mtstate->operation == CMD_MERGE)
        ExecInitMerge(mtstate, estate);
 
    EvalPlanQualSetPlan(&mtstate->mt_epqstate, subplan, arowmarks);
 
    /*
     * If there are a lot of result relations, use a hash table to speed the
     * lookups.  If there are not a lot, a simple linear search is faster.
     *
     * It's not clear where the threshold is, but try 64 for starters.  In a
     * debugging build, use a small threshold so that we get some test
     * coverage of both code paths.
     */
#ifdef USE_ASSERT_CHECKING
#define MT_NRELS_HASH 4
#else
#define MT_NRELS_HASH 64
#endif
    if (nrels >= MT_NRELS_HASH)
    {
        HASHCTL     hash_ctl;
 
        hash_ctl.keysize = sizeof(Oid);
        hash_ctl.entrysize = sizeof(MTTargetRelLookup);
        hash_ctl.hcxt = CurrentMemoryContext;
        mtstate->mt_resultOidHash =
            hash_create("ModifyTable target hash",
                        nrels, &hash_ctl,
                        HASH_ELEM | HASH_BLOBS | HASH_CONTEXT);
        for (i = 0; i < nrels; i++)
        {
            Oid         hashkey;
            MTTargetRelLookup *mtlookup;
            bool        found;
 
            resultRelInfo = &mtstate->resultRelInfo[i];
            hashkey = RelationGetRelid(resultRelInfo->ri_RelationDesc);
            mtlookup = (MTTargetRelLookup *)
                hash_search(mtstate->mt_resultOidHash, &hashkey,
                            HASH_ENTER, &found);
            Assert(!found);
            mtlookup->relationIndex = i;
        }
    }
    else
        mtstate->mt_resultOidHash = NULL;
 
    /*
     * Determine if the FDW supports batch insert and determine the batch size
     * (a FDW may support batching, but it may be disabled for the
     * server/table).
     *
     * We only do this for INSERT, so that for UPDATE/DELETE the batch size
     * remains set to 0.
     */
    if (operation == CMD_INSERT)
    {
        /* insert may only have one relation, inheritance is not expanded */
        Assert(total_nrels == 1);
        resultRelInfo = mtstate->resultRelInfo;
        if (!resultRelInfo->ri_usesFdwDirectModify &&
            resultRelInfo->ri_FdwRoutine != NULL &&
            resultRelInfo->ri_FdwRoutine->GetForeignModifyBatchSize &&
            resultRelInfo->ri_FdwRoutine->ExecForeignBatchInsert)
        {
            resultRelInfo->ri_BatchSize =
                resultRelInfo->ri_FdwRoutine->GetForeignModifyBatchSize(resultRelInfo);
            Assert(resultRelInfo->ri_BatchSize >= 1);
        }
        else
            resultRelInfo->ri_BatchSize = 1;
    }
 
    /*
     * Lastly, if this is not the primary (canSetTag) ModifyTable node, add it
     * to estate->es_auxmodifytables so that it will be run to completion by
     * ExecPostprocessPlan.  (It'd actually work fine to add the primary
     * ModifyTable node too, but there's no need.)  Note the use of lcons not
     * lappend: we need later-initialized ModifyTable nodes to be shut down
     * before earlier ones.  This ensures that we don't throw away RETURNING
     * rows that need to be seen by a later CTE subplan.
     */
    if (!mtstate->canSetTag)
        estate->es_auxmodifytables = lcons(mtstate,
                                           estate->es_auxmodifytables);
 
    return mtstate;
}
 
/* ----------------------------------------------------------------
 *      ExecEndModifyTable
 *
 *      Shuts down the plan.
 *
 *      Returns nothing of interest.
 * ----------------------------------------------------------------
 */
void
ExecEndModifyTable(ModifyTableState *node)
{
    int         i;
 
    /*
     * Allow any FDWs to shut down
     */
    for (i = 0; i < node->mt_nrels; i++)
    {
        int         j;
        ResultRelInfo *resultRelInfo = node->resultRelInfo + i;
 
        if (!resultRelInfo->ri_usesFdwDirectModify &&
            resultRelInfo->ri_FdwRoutine != NULL &&
            resultRelInfo->ri_FdwRoutine->EndForeignModify != NULL)
            resultRelInfo->ri_FdwRoutine->EndForeignModify(node->ps.state,
                                                           resultRelInfo);
 
        /*
         * Cleanup the initialized batch slots. This only matters for FDWs
         * with batching, but the other cases will have ri_NumSlotsInitialized
         * == 0.
         */
        for (j = 0; j < resultRelInfo->ri_NumSlotsInitialized; j++)
        {
            ExecDropSingleTupleTableSlot(resultRelInfo->ri_Slots[j]);
            ExecDropSingleTupleTableSlot(resultRelInfo->ri_PlanSlots[j]);
        }
    }
 
    /*
     * Close all the partitioned tables, leaf partitions, and their indices
     * and release the slot used for tuple routing, if set.
     */
    if (node->mt_partition_tuple_routing)
    {
        ExecCleanupTupleRouting(node, node->mt_partition_tuple_routing);
 
        if (node->mt_root_tuple_slot)
            ExecDropSingleTupleTableSlot(node->mt_root_tuple_slot);
    }
 
    /*
     * Terminate EPQ execution if active
     */
    EvalPlanQualEnd(&node->mt_epqstate);
 
    /*
     * shut down subplan
     */
    ExecEndNode(outerPlanState(node));
}
 
void
ExecReScanModifyTable(ModifyTableState *node)
{
    /*
     * Currently, we don't need to support rescan on ModifyTable nodes. The
     * semantics of that would be a bit debatable anyway.
     */
    elog(ERROR, "ExecReScanModifyTable is not implemented");
}