nodeModifyTable.c

Go to the documentation of this file.

/*-------------------------------------------------------------------------
 *
 * nodeModifyTable.c
 *    routines to handle ModifyTable nodes.
 *
 * Portions Copyright (c) 1996-2020, 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
 *      Each ModifyTable node contains a list of one or more subplans,
 *      much like an Append node.  There is one subplan per result relation.
 *      The key reason for this is that in an inherited UPDATE command, each
 *      result relation could have a different schema (more or different
 *      columns) requiring a different plan tree to produce it.  In an
 *      inherited DELETE, all the subplans should produce the same output
 *      rowtype, but we might still find that different plans are appropriate
 *      for different child relations.
 *
 *      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/heapam.h"
#include "access/htup_details.h"
#include "access/tableam.h"
#include "access/xact.h"
#include "catalog/catalog.h"
#include "commands/trigger.h"
#include "executor/execPartition.h"
#include "executor/executor.h"
#include "executor/nodeModifyTable.h"
#include "foreign/fdwapi.h"
#include "miscadmin.h"
#include "nodes/nodeFuncs.h"
#include "rewrite/rewriteHandler.h"
#include "storage/bufmgr.h"
#include "storage/lmgr.h"
#include "utils/builtins.h"
#include "utils/datum.h"
#include "utils/memutils.h"
#include "utils/rel.h"


static bool ExecOnConflictUpdate(ModifyTableState *mtstate,
                                 ResultRelInfo *resultRelInfo,
                                 ItemPointer conflictTid,
                                 TupleTableSlot *planSlot,
                                 TupleTableSlot *excludedSlot,
                                 EState *estate,
                                 bool canSetTag,
                                 TupleTableSlot **returning);
static TupleTableSlot *ExecPrepareTupleRouting(ModifyTableState *mtstate,
                                               EState *estate,
                                               PartitionTupleRouting *proute,
                                               ResultRelInfo *targetRelInfo,
                                               TupleTableSlot *slot);
static ResultRelInfo *getTargetResultRelInfo(ModifyTableState *node);
static void ExecSetupChildParentMapForSubplan(ModifyTableState *mtstate);
static TupleConversionMap *tupconv_map_for_subplan(ModifyTableState *node,
                                                   int whichplan);

/*
 * Verify that the tuples to be produced by INSERT or UPDATE 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.
 */
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;

        if (tle->resjunk)
            continue;           /* ignore junk tlist items */

        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++;

        if (!attr->attisdropped)
        {
            /* 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)))));
        }
        else
        {
            /*
             * 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)));
        }
    }
    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
 *
 * resultRelInfo: current result rel
 * tupleSlot: slot holding tuple actually inserted/updated/deleted
 * planSlot: slot holding tuple returned by top subplan node
 *
 * Note: If tupleSlot is NULL, the FDW should have already provided econtext's
 * scan tuple.
 *
 * Returns a slot holding the result tuple
 */
static TupleTableSlot *
ExecProcessReturning(ResultRelInfo *resultRelInfo,
                     TupleTableSlot *tupleSlot,
                     TupleTableSlot *planSlot)
{
    ProjectionInfo *projectReturning = resultRelInfo->ri_projectReturning;
    ExprContext *econtext = projectReturning->pi_exprContext;

    /* Make tuple and any needed join variables available to ExecProject */
    if (tupleSlot)
        econtext->ecxt_scantuple = tupleSlot;
    econtext->ecxt_outertuple = planSlot;

    /*
     * RETURNING expressions might reference the tableoid column, so
     * reinitialize tts_tableOid before evaluating them.
     */
    econtext->ecxt_scantuple->tts_tableOid =
        RelationGetRelid(resultRelInfo->ri_RelationDesc);

    /* 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);
}

/*
 * Compute stored generated columns for a tuple
 */
void
ExecComputeStoredGenerated(EState *estate, TupleTableSlot *slot, CmdType cmdtype)
{
    ResultRelInfo *resultRelInfo = estate->es_result_relation_info;
    Relation    rel = resultRelInfo->ri_RelationDesc;
    TupleDesc   tupdesc = RelationGetDescr(rel);
    int         natts = tupdesc->natts;
    MemoryContext oldContext;
    Datum      *values;
    bool       *nulls;

    Assert(tupdesc->constr && tupdesc->constr->has_generated_stored);

    /*
     * If first time through for this result relation, build expression
     * nodetrees for rel's stored generation expressions.  Keep them in the
     * per-query memory context so they'll survive throughout the query.
     */
    if (resultRelInfo->ri_GeneratedExprs == NULL)
    {
        oldContext = MemoryContextSwitchTo(estate->es_query_cxt);

        resultRelInfo->ri_GeneratedExprs =
            (ExprState **) palloc(natts * sizeof(ExprState *));
        resultRelInfo->ri_NumGeneratedNeeded = 0;

        for (int i = 0; i < natts; i++)
        {
            if (TupleDescAttr(tupdesc, i)->attgenerated == ATTRIBUTE_GENERATED_STORED)
            {
                Expr       *expr;

                /*
                 * If it's an update and the current column was not marked as
                 * being updated, then we can skip the computation.  But if
                 * there is a BEFORE ROW UPDATE trigger, we cannot skip
                 * because the trigger might affect additional columns.
                 */
                if (cmdtype == CMD_UPDATE &&
                    !(rel->trigdesc && rel->trigdesc->trig_update_before_row) &&
                    !bms_is_member(i + 1 - FirstLowInvalidHeapAttributeNumber,
                                   exec_rt_fetch(resultRelInfo->ri_RangeTableIndex, estate)->extraUpdatedCols))
                {
                    resultRelInfo->ri_GeneratedExprs[i] = NULL;
                    continue;
                }

                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));

                resultRelInfo->ri_GeneratedExprs[i] = ExecPrepareExpr(expr, estate);
                resultRelInfo->ri_NumGeneratedNeeded++;
            }
        }

        MemoryContextSwitchTo(oldContext);
    }

    /*
     * If no generated columns have been affected by this change, then skip
     * the rest.
     */
    if (resultRelInfo->ri_NumGeneratedNeeded == 0)
        return;

    oldContext = MemoryContextSwitchTo(GetPerTupleMemoryContext(estate));

    values = palloc(sizeof(*values) * natts);
    nulls = palloc(sizeof(*nulls) * natts);

    slot_getallattrs(slot);
    memcpy(nulls, slot->tts_isnull, sizeof(*nulls) * natts);

    for (int i = 0; i < natts; i++)
    {
        Form_pg_attribute attr = TupleDescAttr(tupdesc, i);

        if (attr->attgenerated == ATTRIBUTE_GENERATED_STORED &&
            resultRelInfo->ri_GeneratedExprs[i])
        {
            ExprContext *econtext;
            Datum       val;
            bool        isnull;

            econtext = GetPerTupleExprContext(estate);
            econtext->ecxt_scantuple = slot;

            val = ExecEvalExpr(resultRelInfo->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);
}

/* ----------------------------------------------------------------
 *      ExecInsert
 *
 *      For INSERT, we have to insert the tuple into the target relation
 *      and insert appropriate tuples into the index relations.
 *
 *      Returns RETURNING result if any, otherwise NULL.
 * ----------------------------------------------------------------
 */
static TupleTableSlot *
ExecInsert(ModifyTableState *mtstate,
           TupleTableSlot *slot,
           TupleTableSlot *planSlot,
           EState *estate,
           bool canSetTag)
{
    ResultRelInfo *resultRelInfo;
    Relation    resultRelationDesc;
    List       *recheckIndexes = NIL;
    TupleTableSlot *result = NULL;
    TransitionCaptureState *ar_insert_trig_tcs;
    ModifyTable *node = (ModifyTable *) mtstate->ps.plan;
    OnConflictAction onconflict = node->onConflictAction;

    ExecMaterializeSlot(slot);

    /*
     * get information on the (current) result relation
     */
    resultRelInfo = estate->es_result_relation_info;
    resultRelationDesc = resultRelInfo->ri_RelationDesc;

    /*
     * 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)
    {
        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)
    {
        /*
         * Compute stored generated columns
         */
        if (resultRelationDesc->rd_att->constr &&
            resultRelationDesc->rd_att->constr->has_generated_stored)
            ExecComputeStoredGenerated(estate, slot, CMD_INSERT);

        /*
         * 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.
         */
        slot->tts_tableOid = RelationGetRelid(resultRelInfo->ri_RelationDesc);
    }
    else
    {
        WCOKind     wco_kind;

        /*
         * Constraints 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(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.
         */
        wco_kind = (mtstate->operation == CMD_UPDATE) ?
            WCO_RLS_UPDATE_CHECK : 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 (resultRelInfo->ri_PartitionCheck &&
            (resultRelInfo->ri_PartitionRoot == 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;
            bool        specConflict;
            List       *arbiterIndexes;

            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.
             */
    vlock:
            specConflict = false;
            if (!ExecCheckIndexConstraints(slot, estate, &conflictTid,
                                           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(mtstate, resultRelInfo,
                                             &conflictTid, planSlot, slot,
                                             estate, 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.
             */
            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(slot, estate, true,
                                                   &specConflict,
                                                   arbiterIndexes);

            /* 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(slot, estate, false, NULL,
                                                       NIL);
        }
    }

    if (canSetTag)
    {
        (estate->es_processed)++;
        setLastTid(&slot->tts_tid);
    }

    /*
     * 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,
                             slot,
                             NULL,
                             mtstate->mt_transition_capture);

        /*
         * 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)
        result = ExecProcessReturning(resultRelInfo, slot, planSlot);

    return result;
}

/* ----------------------------------------------------------------
 *      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 from a view,
 *      oldtuple is passed to the INSTEAD OF 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 epqslot.
 *
 *      Returns RETURNING result if any, otherwise NULL.
 * ----------------------------------------------------------------
 */
static TupleTableSlot *
ExecDelete(ModifyTableState *mtstate,
           ItemPointer tupleid,
           HeapTuple oldtuple,
           TupleTableSlot *planSlot,
           EPQState *epqstate,
           EState *estate,
           bool processReturning,
           bool canSetTag,
           bool changingPart,
           bool *tupleDeleted,
           TupleTableSlot **epqreturnslot)
{
    ResultRelInfo *resultRelInfo;
    Relation    resultRelationDesc;
    TM_Result   result;
    TM_FailureData tmfd;
    TupleTableSlot *slot = NULL;
    TransitionCaptureState *ar_delete_trig_tcs;

    if (tupleDeleted)
        *tupleDeleted = false;

    /*
     * get information on the (current) result relation
     */
    resultRelInfo = estate->es_result_relation_info;
    resultRelationDesc = resultRelInfo->ri_RelationDesc;

    /* BEFORE ROW DELETE Triggers */
    if (resultRelInfo->ri_TrigDesc &&
        resultRelInfo->ri_TrigDesc->trig_delete_before_row)
    {
        bool        dodelete;

        dodelete = ExecBRDeleteTriggers(estate, epqstate, resultRelInfo,
                                        tupleid, oldtuple, epqreturnslot);

        if (!dodelete)          /* "do nothing" */
            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,
                                                               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 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 = table_tuple_delete(resultRelationDesc, tupleid,
                                    estate->es_output_cid,
                                    estate->es_snapshot,
                                    estate->es_crosscheck_snapshot,
                                    true /* wait for commit */ ,
                                    &tmfd,
                                    changingPart);

        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 (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(epqstate);
                    inputslot = EvalPlanQualSlot(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,
                                              &tmfd);

                    switch (result)
                    {
                        case TM_Ok:
                            Assert(tmfd.traversed);
                            epqslot = EvalPlanQual(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 (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;

    /*
     * 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,
                             tupleid,
                             oldtuple,
                             NULL,
                             NULL,
                             mtstate->mt_transition_capture);

        /*
         * We've already captured the NEW TABLE row, so make sure any AR
         * DELETE trigger fired below doesn't capture it again.
         */
        ar_delete_trig_tcs = NULL;
    }

    /* AFTER ROW DELETE Triggers */
    ExecARDeleteTriggers(estate, resultRelInfo, tupleid, oldtuple,
                         ar_delete_trig_tcs);

    /* Process RETURNING if present and if requested */
    if (processReturning && resultRelInfo->ri_projectReturning)
    {
        /*
         * 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");
            }
        }

        rslot = ExecProcessReturning(resultRelInfo, slot, 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;
}

/* ----------------------------------------------------------------
 *      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 a view, oldtuple
 *      is passed to the INSTEAD OF 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.
 *
 *      Returns RETURNING result if any, otherwise NULL.
 * ----------------------------------------------------------------
 */
static TupleTableSlot *
ExecUpdate(ModifyTableState *mtstate,
           ItemPointer tupleid,
           HeapTuple oldtuple,
           TupleTableSlot *slot,
           TupleTableSlot *planSlot,
           EPQState *epqstate,
           EState *estate,
           bool canSetTag)
{
    ResultRelInfo *resultRelInfo;
    Relation    resultRelationDesc;
    TM_Result   result;
    TM_FailureData tmfd;
    List       *recheckIndexes = NIL;
    TupleConversionMap *saved_tcs_map = NULL;

    /*
     * abort the operation if not running transactions
     */
    if (IsBootstrapProcessingMode())
        elog(ERROR, "cannot UPDATE during bootstrap");

    ExecMaterializeSlot(slot);

    /*
     * get information on the (current) result relation
     */
    resultRelInfo = estate->es_result_relation_info;
    resultRelationDesc = resultRelInfo->ri_RelationDesc;

    /* BEFORE ROW UPDATE Triggers */
    if (resultRelInfo->ri_TrigDesc &&
        resultRelInfo->ri_TrigDesc->trig_update_before_row)
    {
        if (!ExecBRUpdateTriggers(estate, epqstate, resultRelInfo,
                                  tupleid, oldtuple, slot))
            return NULL;        /* "do nothing" */
    }

    /* 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)
    {
        /*
         * Compute stored generated columns
         */
        if (resultRelationDesc->rd_att->constr &&
            resultRelationDesc->rd_att->constr->has_generated_stored)
            ExecComputeStoredGenerated(estate, slot, CMD_UPDATE);

        /*
         * update in foreign table: let the FDW do it
         */
        slot = resultRelInfo->ri_FdwRoutine->ExecForeignUpdate(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.
         */
        slot->tts_tableOid = RelationGetRelid(resultRelationDesc);
    }
    else
    {
        LockTupleMode lockmode;
        bool        partition_constraint_failed;
        bool        update_indexes;

        /*
         * Constraints 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(estate, slot, CMD_UPDATE);

        /*
         * Check any RLS UPDATE WITH CHECK policies
         *
         * If we generate a new candidate tuple after EvalPlanQual testing, we
         * must loop back here and recheck any RLS policies and constraints.
         * (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.)
         */
lreplace:;

        /* 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 =
            resultRelInfo->ri_PartitionCheck &&
            !ExecPartitionCheck(resultRelInfo, slot, estate, false);

        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)
        {
            bool        tuple_deleted;
            TupleTableSlot *ret_slot;
            TupleTableSlot *epqslot = NULL;
            PartitionTupleRouting *proute = mtstate->mt_partition_tuple_routing;
            int         map_index;
            TupleConversionMap *tupconv_map;

            /*
             * 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 on a leaf partition, we will not have
             * partition tuple routing set up. In that case, fail with
             * partition constraint violation error.
             */
            if (proute == NULL)
                ExecPartitionCheckEmitError(resultRelInfo, slot, estate);

            /*
             * Row movement, part 1.  Delete the tuple, but skip RETURNING
             * processing. We want to return rows from INSERT.
             */
            ExecDelete(mtstate, tupleid, oldtuple, planSlot, epqstate,
                       estate, false, false /* canSetTag */ ,
                       true /* changingPart */ , &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.
                 */
                if (TupIsNull(epqslot))
                    return NULL;
                else
                {
                    slot = ExecFilterJunk(resultRelInfo->ri_junkFilter, epqslot);
                    goto lreplace;
                }
            }

            /*
             * Updates set the transition capture map only when a new subplan
             * is chosen.  But for inserts, it is set for each row. So after
             * INSERT, we need to revert back to the map created for UPDATE;
             * otherwise the next UPDATE will incorrectly use the one created
             * for INSERT.  So first save the one created for UPDATE.
             */
            if (mtstate->mt_transition_capture)
                saved_tcs_map = mtstate->mt_transition_capture->tcs_map;

            /*
             * resultRelInfo is one of the per-subplan resultRelInfos.  So we
             * should convert the tuple into root's tuple descriptor, since
             * ExecInsert() starts the search from root.  The tuple conversion
             * map list is in the order of mtstate->resultRelInfo[], so to
             * retrieve the one for this resultRel, we need to know the
             * position of the resultRel in mtstate->resultRelInfo[].
             */
            map_index = resultRelInfo - mtstate->resultRelInfo;
            Assert(map_index >= 0 && map_index < mtstate->mt_nplans);
            tupconv_map = tupconv_map_for_subplan(mtstate, map_index);
            if (tupconv_map != NULL)
                slot = execute_attr_map_slot(tupconv_map->attrMap,
                                             slot,
                                             mtstate->mt_root_tuple_slot);

            /*
             * Prepare for tuple routing, making it look like we're inserting
             * into the root.
             */
            Assert(mtstate->rootResultRelInfo != NULL);
            slot = ExecPrepareTupleRouting(mtstate, estate, proute,
                                           mtstate->rootResultRelInfo, slot);

            ret_slot = ExecInsert(mtstate, slot, planSlot,
                                  estate, canSetTag);

            /* Revert ExecPrepareTupleRouting's node change. */
            estate->es_result_relation_info = resultRelInfo;
            if (mtstate->mt_transition_capture)
            {
                mtstate->mt_transition_capture->tcs_original_insert_tuple = NULL;
                mtstate->mt_transition_capture->tcs_map = saved_tcs_map;
            }

            return ret_slot;
        }

        /*
         * 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,
                                    estate->es_snapshot,
                                    estate->es_crosscheck_snapshot,
                                    true /* wait for commit */ ,
                                    &tmfd, &lockmode, &update_indexes);

        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 (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(epqstate, resultRelationDesc,
                                                 resultRelInfo->ri_RangeTableIndex);

                    result = table_tuple_lock(resultRelationDesc, tupleid,
                                              estate->es_snapshot,
                                              inputslot, estate->es_output_cid,
                                              lockmode, LockWaitBlock,
                                              TUPLE_LOCK_FLAG_FIND_LAST_VERSION,
                                              &tmfd);

                    switch (result)
                    {
                        case TM_Ok:
                            Assert(tmfd.traversed);

                            epqslot = EvalPlanQual(epqstate,
                                                   resultRelationDesc,
                                                   resultRelInfo->ri_RangeTableIndex,
                                                   inputslot);
                            if (TupIsNull(epqslot))
                                /* Tuple not passing quals anymore, exiting... */
                                return NULL;

                            slot = ExecFilterJunk(resultRelInfo->ri_junkFilter, epqslot);
                            goto lreplace;

                        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 (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;
        }

        /* insert index entries for tuple if necessary */
        if (resultRelInfo->ri_NumIndices > 0 && update_indexes)
            recheckIndexes = ExecInsertIndexTuples(slot, estate, false, NULL, NIL);
    }

    if (canSetTag)
        (estate->es_processed)++;

    /* AFTER ROW UPDATE Triggers */
    ExecARUpdateTriggers(estate, resultRelInfo, tupleid, oldtuple, slot,
                         recheckIndexes,
                         mtstate->operation == CMD_INSERT ?
                         mtstate->mt_oc_transition_capture :
                         mtstate->mt_transition_capture);

    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, estate);

    /* Process RETURNING if present */
    if (resultRelInfo->ri_projectReturning)
        return ExecProcessReturning(resultRelInfo, slot, planSlot);

    return NULL;
}

/*
 * 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(ModifyTableState *mtstate,
                     ResultRelInfo *resultRelInfo,
                     ItemPointer conflictTid,
                     TupleTableSlot *planSlot,
                     TupleTableSlot *excludedSlot,
                     EState *estate,
                     bool canSetTag,
                     TupleTableSlot **returning)
{
    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;
    TM_FailureData tmfd;
    LockTupleMode lockmode;
    TM_Result   test;
    Datum       xminDatum;
    TransactionId xmin;
    bool        isnull;

    /* Determine lock mode to use */
    lockmode = ExecUpdateLockMode(estate, resultRelInfo);

    /*
     * Lock tuple for update.  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,
                            estate->es_snapshot,
                            existing, 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 SQL-2003 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),
                         errmsg("ON CONFLICT DO UPDATE command cannot affect row a second time"),
                         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")));

            /*
             * As long as we don't support an UPDATE of INSERT ON CONFLICT for
             * a partitioned table we shouldn't reach to a case where tuple to
             * be lock is moved to another partition due to concurrent update
             * of the partition key.
             */
            Assert(!ItemPointerIndicatesMovedPartitions(&tmfd.ctid));

            /*
             * 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 */
            Assert(!ItemPointerIndicatesMovedPartitions(&tmfd.ctid));
            ExecClearTuple(existing);
            return false;

        default:
            elog(ERROR, "unrecognized table_tuple_lock status: %u", test);
    }

    /* Success, the tuple is locked. */

    /*
     * 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(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,
         * but that's almost the extent of its special handling for ON
         * CONFLICT DO UPDATE.
         *
         * 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(mtstate, conflictTid, NULL,
                            resultRelInfo->ri_onConflict->oc_ProjSlot,
                            planSlot,
                            &mtstate->mt_epqstate, mtstate->ps.state,
                            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.
     */
    ExecClearTuple(existing);
    return true;
}


/*
 * Process BEFORE EACH STATEMENT triggers
 */
static void
fireBSTriggers(ModifyTableState *node)
{
    ModifyTable *plan = (ModifyTable *) node->ps.plan;
    ResultRelInfo *resultRelInfo = node->resultRelInfo;

    /*
     * If the node modifies a partitioned table, we must fire its triggers.
     * Note that in that case, node->resultRelInfo points to the first leaf
     * partition, not the root table.
     */
    if (node->rootResultRelInfo != NULL)
        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;
        default:
            elog(ERROR, "unknown operation");
            break;
    }
}

/*
 * Return the target rel ResultRelInfo.
 *
 * This relation is the same as :
 * - the relation for which we will fire AFTER STATEMENT triggers.
 * - the relation into whose tuple format all captured transition tuples must
 *   be converted.
 * - the root partitioned table.
 */
static ResultRelInfo *
getTargetResultRelInfo(ModifyTableState *node)
{
    /*
     * Note that if the node modifies a partitioned table, node->resultRelInfo
     * points to the first leaf partition, not the root table.
     */
    if (node->rootResultRelInfo != NULL)
        return node->rootResultRelInfo;
    else
        return node->resultRelInfo;
}

/*
 * Process AFTER EACH STATEMENT triggers
 */
static void
fireASTriggers(ModifyTableState *node)
{
    ModifyTable *plan = (ModifyTable *) node->ps.plan;
    ResultRelInfo *resultRelInfo = getTargetResultRelInfo(node);

    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;
        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 = getTargetResultRelInfo(mtstate);

    /* 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);

    /*
     * If we found that we need to collect transition tuples then we may also
     * need tuple conversion maps for any children that have TupleDescs that
     * aren't compatible with the tuplestores.  (We can share these maps
     * between the regular and ON CONFLICT cases.)
     */
    if (mtstate->mt_transition_capture != NULL ||
        mtstate->mt_oc_transition_capture != NULL)
    {
        ExecSetupChildParentMapForSubplan(mtstate);

        /*
         * Install the conversion map for the first plan for UPDATE and DELETE
         * operations.  It will be advanced each time we switch to the next
         * plan.  (INSERT operations set it every time, so we need not update
         * mtstate->mt_oc_transition_capture here.)
         */
        if (mtstate->mt_transition_capture && mtstate->operation != CMD_INSERT)
            mtstate->mt_transition_capture->tcs_map =
                tupconv_map_for_subplan(mtstate, 0);
    }
}

/*
 * ExecPrepareTupleRouting --- prepare for routing one tuple
 *
 * Determine the partition in which the tuple in slot is to be inserted,
 * and modify mtstate and estate to prepare for it.
 *
 * Caller must revert the estate changes after executing the insertion!
 * In mtstate, transition capture changes may also need to be reverted.
 *
 * Returns a slot holding the tuple of the partition rowtype.
 */
static TupleTableSlot *
ExecPrepareTupleRouting(ModifyTableState *mtstate,
                        EState *estate,
                        PartitionTupleRouting *proute,
                        ResultRelInfo *targetRelInfo,
                        TupleTableSlot *slot)
{
    ResultRelInfo *partrel;
    PartitionRoutingInfo *partrouteinfo;
    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);
    partrouteinfo = partrel->ri_PartitionInfo;
    Assert(partrouteinfo != NULL);

    /*
     * Make it look like we are inserting into the partition.
     */
    estate->es_result_relation_info = partrel;

    /*
     * If we're capturing transition tuples, we might need to convert from the
     * partition rowtype to root partitioned table's rowtype.
     */
    if (mtstate->mt_transition_capture != NULL)
    {
        if (partrel->ri_TrigDesc &&
            partrel->ri_TrigDesc->trig_insert_before_row)
        {
            /*
             * If there are any BEFORE triggers on the partition, we'll have
             * to be ready to convert their result back to tuplestore format.
             */
            mtstate->mt_transition_capture->tcs_original_insert_tuple = NULL;
            mtstate->mt_transition_capture->tcs_map =
                partrouteinfo->pi_PartitionToRootMap;
        }
        else
        {
            /*
             * Otherwise, just remember the original unconverted tuple, to
             * avoid a needless round trip conversion.
             */
            mtstate->mt_transition_capture->tcs_original_insert_tuple = slot;
            mtstate->mt_transition_capture->tcs_map = NULL;
        }
    }
    if (mtstate->mt_oc_transition_capture != NULL)
    {
        mtstate->mt_oc_transition_capture->tcs_map =
            partrouteinfo->pi_PartitionToRootMap;
    }

    /*
     * Convert the tuple, if necessary.
     */
    map = partrouteinfo->pi_RootToPartitionMap;
    if (map != NULL)
    {
        TupleTableSlot *new_slot = partrouteinfo->pi_PartitionTupleSlot;

        slot = execute_attr_map_slot(map->attrMap, slot, new_slot);
    }

    return slot;
}

/*
 * Initialize the child-to-root tuple conversion map array for UPDATE subplans.
 *
 * This map array is required to convert the tuple from the subplan result rel
 * to the target table descriptor. This requirement arises for two independent
 * scenarios:
 * 1. For update-tuple-routing.
 * 2. For capturing tuples in transition tables.
 */
static void
ExecSetupChildParentMapForSubplan(ModifyTableState *mtstate)
{
    ResultRelInfo *targetRelInfo = getTargetResultRelInfo(mtstate);
    ResultRelInfo *resultRelInfos = mtstate->resultRelInfo;
    TupleDesc   outdesc;
    int         numResultRelInfos = mtstate->mt_nplans;
    int         i;

    /*
     * Build array of conversion maps from each child's TupleDesc to the one
     * used in the target relation.  The map pointers may be NULL when no
     * conversion is necessary, which is hopefully a common case.
     */

    /* Get tuple descriptor of the target rel. */
    outdesc = RelationGetDescr(targetRelInfo->ri_RelationDesc);

    mtstate->mt_per_subplan_tupconv_maps = (TupleConversionMap **)
        palloc(sizeof(TupleConversionMap *) * numResultRelInfos);

    for (i = 0; i < numResultRelInfos; ++i)
    {
        mtstate->mt_per_subplan_tupconv_maps[i] =
            convert_tuples_by_name(RelationGetDescr(resultRelInfos[i].ri_RelationDesc),
                                   outdesc);
    }
}

/*
 * For a given subplan index, get the tuple conversion map.
 */
static TupleConversionMap *
tupconv_map_for_subplan(ModifyTableState *mtstate, int whichplan)
{
    /* If nobody else set the per-subplan array of maps, do so ourselves. */
    if (mtstate->mt_per_subplan_tupconv_maps == NULL)
        ExecSetupChildParentMapForSubplan(mtstate);

    Assert(whichplan >= 0 && whichplan < mtstate->mt_nplans);
    return mtstate->mt_per_subplan_tupconv_maps[whichplan];
}

/* ----------------------------------------------------------------
 *     ExecModifyTable
 *
 *      Perform table modifications as required, and return RETURNING results
 *      if needed.
 * ----------------------------------------------------------------
 */
static TupleTableSlot *
ExecModifyTable(PlanState *pstate)
{
    ModifyTableState *node = castNode(ModifyTableState, pstate);
    PartitionTupleRouting *proute = node->mt_partition_tuple_routing;
    EState     *estate = node->ps.state;
    CmdType     operation = node->operation;
    ResultRelInfo *saved_resultRelInfo;
    ResultRelInfo *resultRelInfo;
    PlanState  *subplanstate;
    JunkFilter *junkfilter;
    TupleTableSlot *slot;
    TupleTableSlot *planSlot;
    ItemPointer tupleid;
    ItemPointerData tuple_ctid;
    HeapTupleData oldtupdata;
    HeapTuple   oldtuple;

    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_whichplan;
    subplanstate = node->mt_plans[node->mt_whichplan];
    junkfilter = resultRelInfo->ri_junkFilter;

    /*
     * es_result_relation_info must point to the currently active result
     * relation while we are within this ModifyTable node.  Even though
     * ModifyTable nodes can't be nested statically, they can be nested
     * dynamically (since our subplan could include a reference to a modifying
     * CTE).  So we have to save and restore the caller's value.
     */
    saved_resultRelInfo = estate->es_result_relation_info;

    estate->es_result_relation_info = resultRelInfo;

    /*
     * Fetch rows from subplan(s), 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);

        planSlot = ExecProcNode(subplanstate);

        if (TupIsNull(planSlot))
        {
            /* advance to next subplan if any */
            node->mt_whichplan++;
            if (node->mt_whichplan < node->mt_nplans)
            {
                resultRelInfo++;
                subplanstate = node->mt_plans[node->mt_whichplan];
                junkfilter = resultRelInfo->ri_junkFilter;
                estate->es_result_relation_info = resultRelInfo;
                EvalPlanQualSetPlan(&node->mt_epqstate, subplanstate->plan,
                                    node->mt_arowmarks[node->mt_whichplan]);
                /* Prepare to convert transition tuples from this child. */
                if (node->mt_transition_capture != NULL)
                {
                    node->mt_transition_capture->tcs_map =
                        tupconv_map_for_subplan(node, node->mt_whichplan);
                }
                if (node->mt_oc_transition_capture != NULL)
                {
                    node->mt_oc_transition_capture->tcs_map =
                        tupconv_map_for_subplan(node, node->mt_whichplan);
                }
                continue;
            }
            else
                break;
        }

        /*
         * Ensure input tuple is the right format for the target relation.
         */
        if (node->mt_scans[node->mt_whichplan]->tts_ops != planSlot->tts_ops)
        {
            ExecCopySlot(node->mt_scans[node->mt_whichplan], planSlot);
            planSlot = node->mt_scans[node->mt_whichplan];
        }

        /*
         * 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.
             */
            slot = ExecProcessReturning(resultRelInfo, NULL, planSlot);

            estate->es_result_relation_info = saved_resultRelInfo;
            return slot;
        }

        EvalPlanQualSetSlot(&node->mt_epqstate, planSlot);
        slot = planSlot;

        tupleid = NULL;
        oldtuple = NULL;
        if (junkfilter != NULL)
        {
            /*
             * extract the 'ctid' or 'wholerow' junk attribute.
             */
            if (operation == CMD_UPDATE || operation == CMD_DELETE)
            {
                char        relkind;
                Datum       datum;
                bool        isNull;

                relkind = resultRelInfo->ri_RelationDesc->rd_rel->relkind;
                if (relkind == RELKIND_RELATION || relkind == RELKIND_MATVIEW)
                {
                    datum = ExecGetJunkAttribute(slot,
                                                 junkfilter->jf_junkAttNo,
                                                 &isNull);
                    /* shouldn't ever get a null result... */
                    if (isNull)
                        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.
                 *
                 * Foreign table updates have a wholerow attribute when the
                 * relation has a row-level trigger.  Note that the wholerow
                 * attribute does not carry system columns.  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(junkfilter->jf_junkAttNo))
                {
                    datum = ExecGetJunkAttribute(slot,
                                                 junkfilter->jf_junkAttNo,
                                                 &isNull);
                    /* shouldn't ever get a null result... */
                    if (isNull)
                        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
                    Assert(relkind == RELKIND_FOREIGN_TABLE);
            }

            /*
             * apply the junkfilter if needed.
             */
            if (operation != CMD_DELETE)
                slot = ExecFilterJunk(junkfilter, slot);
        }

        switch (operation)
        {
            case CMD_INSERT:
                /* Prepare for tuple routing if needed. */
                if (proute)
                    slot = ExecPrepareTupleRouting(node, estate, proute,
                                                   resultRelInfo, slot);
                slot = ExecInsert(node, slot, planSlot,
                                  estate, node->canSetTag);
                /* Revert ExecPrepareTupleRouting's state change. */
                if (proute)
                    estate->es_result_relation_info = resultRelInfo;
                break;
            case CMD_UPDATE:
                slot = ExecUpdate(node, tupleid, oldtuple, slot, planSlot,
                                  &node->mt_epqstate, estate, node->canSetTag);
                break;
            case CMD_DELETE:
                slot = ExecDelete(node, tupleid, oldtuple, planSlot,
                                  &node->mt_epqstate, estate,
                                  true, node->canSetTag,
                                  false /* changingPart */ , NULL, NULL);
                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)
        {
            estate->es_result_relation_info = saved_resultRelInfo;
            return slot;
        }
    }

    /* Restore es_result_relation_info before exiting */
    estate->es_result_relation_info = saved_resultRelInfo;

    /*
     * We're done, but fire AFTER STATEMENT triggers before exiting.
     */
    fireASTriggers(node);

    node->mt_done = true;

    return NULL;
}

/* ----------------------------------------------------------------
 *      ExecInitModifyTable
 * ----------------------------------------------------------------
 */
ModifyTableState *
ExecInitModifyTable(ModifyTable *node, EState *estate, int eflags)
{
    ModifyTableState *mtstate;
    CmdType     operation = node->operation;
    int         nplans = list_length(node->plans);
    ResultRelInfo *saved_resultRelInfo;
    ResultRelInfo *resultRelInfo;
    Plan       *subplan;
    ListCell   *l;
    int         i;
    Relation    rel;
    bool        update_tuple_routing_needed = node->partColsUpdated;

    /* check for unsupported flags */
    Assert(!(eflags & (EXEC_FLAG_BACKWARD | EXEC_FLAG_MARK)));

    /*
     * 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_plans = (PlanState **) palloc0(sizeof(PlanState *) * nplans);
    mtstate->resultRelInfo = estate->es_result_relations + node->resultRelIndex;
    mtstate->mt_scans = (TupleTableSlot **) palloc0(sizeof(TupleTableSlot *) * nplans);

    /* If modifying a partitioned table, initialize the root table info */
    if (node->rootResultRelIndex >= 0)
        mtstate->rootResultRelInfo = estate->es_root_result_relations +
            node->rootResultRelIndex;

    mtstate->mt_arowmarks = (List **) palloc0(sizeof(List *) * nplans);
    mtstate->mt_nplans = nplans;

    /* set up epqstate with dummy subplan data for the moment */
    EvalPlanQualInit(&mtstate->mt_epqstate, estate, NULL, NIL, node->epqParam);
    mtstate->fireBSTriggers = true;

    /*
     * call ExecInitNode on each of the plans to be executed and save the
     * results into the array "mt_plans".  This is also a convenient place to
     * verify that the proposed target relations are valid and open their
     * indexes for insertion of new index entries.  Note we *must* set
     * estate->es_result_relation_info correctly while we initialize each
     * sub-plan; external modules such as FDWs may depend on that (see
     * contrib/postgres_fdw/postgres_fdw.c: postgresBeginDirectModify() as one
     * example).
     */
    saved_resultRelInfo = estate->es_result_relation_info;

    resultRelInfo = mtstate->resultRelInfo;
    i = 0;
    foreach(l, node->plans)
    {
        subplan = (Plan *) lfirst(l);

        /* 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);

        /*
         * If there are indices on the result relation, open them and save
         * descriptors in the result relation info, so that we can add new
         * index entries for the tuples we add/update.  We need not do this
         * for a DELETE, however, since deletion doesn't affect indexes. Also,
         * inside an EvalPlanQual operation, the indexes might be open
         * already, since we share the resultrel state with the original
         * query.
         */
        if (resultRelInfo->ri_RelationDesc->rd_rel->relhasindex &&
            operation != CMD_DELETE &&
            resultRelInfo->ri_IndexRelationDescs == NULL)
            ExecOpenIndices(resultRelInfo,
                            node->onConflictAction != ONCONFLICT_NONE);

        /*
         * If this is an UPDATE and a BEFORE UPDATE trigger is present, the
         * trigger itself might modify the partition-key values. So arrange
         * for tuple routing.
         */
        if (resultRelInfo->ri_TrigDesc &&
            resultRelInfo->ri_TrigDesc->trig_update_before_row &&
            operation == CMD_UPDATE)
            update_tuple_routing_needed = true;

        /* Now init the plan for this result rel */
        estate->es_result_relation_info = resultRelInfo;
        mtstate->mt_plans[i] = ExecInitNode(subplan, estate, eflags);
        mtstate->mt_scans[i] =
            ExecInitExtraTupleSlot(mtstate->ps.state, ExecGetResultType(mtstate->mt_plans[i]),
                                   table_slot_callbacks(resultRelInfo->ri_RelationDesc));

        /* Also 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);
        }

        resultRelInfo++;
        i++;
    }

    estate->es_result_relation_info = saved_resultRelInfo;

    /* Get the target relation */
    rel = (getTargetResultRelInfo(mtstate))->ri_RelationDesc;

    /*
     * If it's not a partitioned table after all, UPDATE tuple routing should
     * not be attempted.
     */
    if (rel->rd_rel->relkind != RELKIND_PARTITIONED_TABLE)
        update_tuple_routing_needed = false;

    /*
     * Build state for tuple routing if it's an INSERT or if it's an UPDATE of
     * partition key.
     */
    if (rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE &&
        (operation == CMD_INSERT || update_tuple_routing_needed))
        mtstate->mt_partition_tuple_routing =
            ExecSetupPartitionTupleRouting(estate, mtstate, rel);

    /*
     * 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);

    /*
     * Construct mapping from each of the per-subplan partition attnos to the
     * root attno.  This is required when during update row movement the tuple
     * descriptor of a source partition does not match the root partitioned
     * table descriptor.  In such a case we need to convert tuples to the root
     * tuple descriptor, because the search for destination partition starts
     * from the root.  We'll also need a slot to store these converted tuples.
     * We can skip this setup if it's not a partition key update.
     */
    if (update_tuple_routing_needed)
    {
        ExecSetupChildParentMapForSubplan(mtstate);
        mtstate->mt_root_tuple_slot = table_slot_create(rel, NULL);
    }

    /*
     * Initialize any WITH CHECK OPTION constraints if needed.
     */
    resultRelInfo = mtstate->resultRelInfo;
    i = 0;
    foreach(l, node->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++;
        i++;
    }

    /*
     * Initialize RETURNING projections if needed.
     */
    if (node->returningLists)
    {
        TupleTableSlot *slot;
        ExprContext *econtext;

        /*
         * Initialize result tuple slot and assign its rowtype using the first
         * RETURNING list.  We assume the rest will look the same.
         */
        mtstate->ps.plan->targetlist = (List *) linitial(node->returningLists);

        /* Set up a slot for the output of the RETURNING projection(s) */
        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, node->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?).
         */
        mtstate->ps.plan->targetlist = NIL;
        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)
        resultRelInfo->ri_onConflictArbiterIndexes = node->arbiterIndexes;

    /*
     * If needed, Initialize target list, projection and qual for ON CONFLICT
     * DO UPDATE.
     */
    if (node->onConflictAction == ONCONFLICT_UPDATE)
    {
        ExprContext *econtext;
        TupleDesc   relationDesc;
        TupleDesc   tupDesc;

        /* insert may only have one plan, inheritance is not expanded */
        Assert(nplans == 1);

        /* already exists if created by RETURNING processing above */
        if (mtstate->ps.ps_ExprContext == NULL)
            ExecAssignExprContext(estate, &mtstate->ps);

        econtext = mtstate->ps.ps_ExprContext;
        relationDesc = resultRelInfo->ri_RelationDesc->rd_att;

        /* create state for DO UPDATE SET operation */
        resultRelInfo->ri_onConflict = makeNode(OnConflictSetState);

        /* initialize slot for the existing tuple */
        resultRelInfo->ri_onConflict->oc_Existing =
            table_slot_create(resultRelInfo->ri_RelationDesc,
                              &mtstate->ps.state->es_tupleTable);

        /*
         * 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.
         */
        tupDesc = ExecTypeFromTL((List *) node->onConflictSet);
        resultRelInfo->ri_onConflict->oc_ProjSlot =
            ExecInitExtraTupleSlot(mtstate->ps.state, tupDesc,
                                   table_slot_callbacks(resultRelInfo->ri_RelationDesc));

        /* build UPDATE SET projection state */
        resultRelInfo->ri_onConflict->oc_ProjInfo =
            ExecBuildProjectionInfo(node->onConflictSet, econtext,
                                    resultRelInfo->ri_onConflict->oc_ProjSlot,
                                    &mtstate->ps,
                                    relationDesc);

        /* initialize state to evaluate the WHERE clause, if any */
        if (node->onConflictWhere)
        {
            ExprState  *qualexpr;

            qualexpr = ExecInitQual((List *) node->onConflictWhere,
                                    &mtstate->ps);
            resultRelInfo->ri_onConflict->oc_WhereClause = qualexpr;
        }
    }

    /*
     * If we have any secondary relations in an UPDATE or DELETE, they need to
     * be treated like non-locked relations in SELECT FOR UPDATE, ie, the
     * EvalPlanQual mechanism needs to be told about them.  Locate the
     * relevant ExecRowMarks.
     */
    foreach(l, node->rowMarks)
    {
        PlanRowMark *rc = lfirst_node(PlanRowMark, l);
        ExecRowMark *erm;

        /* ignore "parent" rowmarks; they are irrelevant at runtime */
        if (rc->isParent)
            continue;

        /* find ExecRowMark (same for all subplans) */
        erm = ExecFindRowMark(estate, rc->rti, false);

        /* build ExecAuxRowMark for each subplan */
        for (i = 0; i < nplans; i++)
        {
            ExecAuxRowMark *aerm;

            subplan = mtstate->mt_plans[i]->plan;
            aerm = ExecBuildAuxRowMark(erm, subplan->targetlist);
            mtstate->mt_arowmarks[i] = lappend(mtstate->mt_arowmarks[i], aerm);
        }
    }

    /* select first subplan */
    mtstate->mt_whichplan = 0;
    subplan = (Plan *) linitial(node->plans);
    EvalPlanQualSetPlan(&mtstate->mt_epqstate, subplan,
                        mtstate->mt_arowmarks[0]);

    /*
     * Initialize the junk filter(s) if needed.  INSERT queries need a filter
     * if there are any junk attrs in the tlist.  UPDATE and DELETE always
     * need a filter, since there's always at least one junk attribute present
     * --- no need to look first.  Typically, this will be a 'ctid' or
     * 'wholerow' attribute, but in the case of a foreign data wrapper it
     * might be a set of junk attributes sufficient to identify the remote
     * row.
     *
     * If there are multiple result relations, each one needs its own junk
     * filter.  Note multiple rels are only possible for UPDATE/DELETE, so we
     * can't be fooled by some needing a filter and some not.
     *
     * This section of code is also a convenient place to verify that the
     * output of an INSERT or UPDATE matches the target table(s).
     */
    {
        bool        junk_filter_needed = false;

        switch (operation)
        {
            case CMD_INSERT:
                foreach(l, subplan->targetlist)
                {
                    TargetEntry *tle = (TargetEntry *) lfirst(l);

                    if (tle->resjunk)
                    {
                        junk_filter_needed = true;
                        break;
                    }
                }
                break;
            case CMD_UPDATE:
            case CMD_DELETE:
                junk_filter_needed = true;
                break;
            default:
                elog(ERROR, "unknown operation");
                break;
        }

        if (junk_filter_needed)
        {
            resultRelInfo = mtstate->resultRelInfo;
            for (i = 0; i < nplans; i++)
            {
                JunkFilter *j;
                TupleTableSlot *junkresslot;

                subplan = mtstate->mt_plans[i]->plan;
                if (operation == CMD_INSERT || operation == CMD_UPDATE)
                    ExecCheckPlanOutput(resultRelInfo->ri_RelationDesc,
                                        subplan->targetlist);

                junkresslot =
                    ExecInitExtraTupleSlot(estate, NULL,
                                           table_slot_callbacks(resultRelInfo->ri_RelationDesc));
                j = ExecInitJunkFilter(subplan->targetlist,
                                       junkresslot);

                if (operation == CMD_UPDATE || operation == CMD_DELETE)
                {
                    /* For UPDATE/DELETE, find the appropriate junk attr now */
                    char        relkind;

                    relkind = resultRelInfo->ri_RelationDesc->rd_rel->relkind;
                    if (relkind == RELKIND_RELATION ||
                        relkind == RELKIND_MATVIEW ||
                        relkind == RELKIND_PARTITIONED_TABLE)
                    {
                        j->jf_junkAttNo = ExecFindJunkAttribute(j, "ctid");
                        if (!AttributeNumberIsValid(j->jf_junkAttNo))
                            elog(ERROR, "could not find junk ctid column");
                    }
                    else if (relkind == RELKIND_FOREIGN_TABLE)
                    {
                        /*
                         * When there is a row-level trigger, there should be
                         * a wholerow attribute.
                         */
                        j->jf_junkAttNo = ExecFindJunkAttribute(j, "wholerow");
                    }
                    else
                    {
                        j->jf_junkAttNo = ExecFindJunkAttribute(j, "wholerow");
                        if (!AttributeNumberIsValid(j->jf_junkAttNo))
                            elog(ERROR, "could not find junk wholerow column");
                    }
                }

                resultRelInfo->ri_junkFilter = j;
                resultRelInfo++;
            }
        }
        else
        {
            if (operation == CMD_INSERT)
                ExecCheckPlanOutput(mtstate->resultRelInfo->ri_RelationDesc,
                                    subplan->targetlist);
        }
    }

    /*
     * 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_nplans; i++)
    {
        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);
    }

    /*
     * 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);
    }

    /*
     * Free the exprcontext
     */
    ExecFreeExprContext(&node->ps);

    /*
     * clean out the tuple table
     */
    if (node->ps.ps_ResultTupleSlot)
        ExecClearTuple(node->ps.ps_ResultTupleSlot);

    /*
     * Terminate EPQ execution if active
     */
    EvalPlanQualEnd(&node->mt_epqstate);

    /*
     * shut down subplans
     */
    for (i = 0; i < node->mt_nplans; i++)
        ExecEndNode(node->mt_plans[i]);
}

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");
}