nodeModifyTable.c

Go to the documentation of this file.

/*-------------------------------------------------------------------------
 *
 * nodeModifyTable.c
 *    routines to handle ModifyTable nodes.
 *
 * Portions Copyright (c) 1996-2017, 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/htup_details.h"
#include "access/xact.h"
#include "commands/trigger.h"
#include "executor/executor.h"
#include "executor/nodeModifyTable.h"
#include "foreign/fdwapi.h"
#include "miscadmin.h"
#include "nodes/nodeFuncs.h"
#include "parser/parsetree.h"
#include "storage/bufmgr.h"
#include "storage/lmgr.h"
#include "utils/builtins.h"
#include "utils/memutils.h"
#include "utils/rel.h"
#include "utils/tqual.h"


static bool ExecOnConflictUpdate(ModifyTableState *mtstate,
                     ResultRelInfo *resultRelInfo,
                     ItemPointer conflictTid,
                     TupleTableSlot *planSlot,
                     TupleTableSlot *excludedSlot,
                     EState *estate,
                     bool canSetTag,
                     TupleTableSlot **returning);

/*
 * 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 = resultDesc->attrs[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
 *
 * projectReturning: RETURNING projection info for 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;

    /*
     * Reset per-tuple memory context to free any expression evaluation
     * storage allocated in the previous cycle.
     */
    ResetExprContext(econtext);

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

        /*
         * RETURNING expressions might reference the tableoid column, so
         * initialize t_tableOid before evaluating them.
         */
        Assert(!TupIsNull(econtext->ecxt_scantuple));
        tuple = ExecMaterializeSlot(econtext->ecxt_scantuple);
        tuple->t_tableOid = RelationGetRelid(resultRelInfo->ri_RelationDesc);
    }
    econtext->ecxt_outertuple = planSlot;

    /* Compute the RETURNING expressions */
    return ExecProject(projectReturning);
}

/*
 * ExecCheckHeapTupleVisible -- verify heap 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
ExecCheckHeapTupleVisible(EState *estate,
                          HeapTuple tuple,
                          Buffer buffer)
{
    if (!IsolationUsesXactSnapshot())
        return;

    /*
     * We need buffer pin and lock to call HeapTupleSatisfiesVisibility.
     * Caller should be holding pin, but not lock.
     */
    LockBuffer(buffer, BUFFER_LOCK_SHARE);
    if (!HeapTupleSatisfiesVisibility(tuple, estate->es_snapshot, buffer))
    {
        /*
         * 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(HeapTupleHeaderGetXmin(tuple->t_data)))
            ereport(ERROR,
                    (errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
                     errmsg("could not serialize access due to concurrent update")));
    }
    LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
}

/*
 * ExecCheckTIDVisible -- convenience variant of ExecCheckHeapTupleVisible()
 */
static void
ExecCheckTIDVisible(EState *estate,
                    ResultRelInfo *relinfo,
                    ItemPointer tid)
{
    Relation    rel = relinfo->ri_RelationDesc;
    Buffer      buffer;
    HeapTupleData tuple;

    /* Redundantly check isolation level */
    if (!IsolationUsesXactSnapshot())
        return;

    tuple.t_self = *tid;
    if (!heap_fetch(rel, SnapshotAny, &tuple, &buffer, false, NULL))
        elog(ERROR, "failed to fetch conflicting tuple for ON CONFLICT");
    ExecCheckHeapTupleVisible(estate, &tuple, buffer);
    ReleaseBuffer(buffer);
}

/* ----------------------------------------------------------------
 *      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,
           List *arbiterIndexes,
           OnConflictAction onconflict,
           EState *estate,
           bool canSetTag)
{
    HeapTuple   tuple;
    ResultRelInfo *resultRelInfo;
    ResultRelInfo *saved_resultRelInfo = NULL;
    Relation    resultRelationDesc;
    Oid         newId;
    List       *recheckIndexes = NIL;
    TupleTableSlot *result = NULL;

    /*
     * get the heap tuple out of the tuple table slot, making sure we have a
     * writable copy
     */
    tuple = ExecMaterializeSlot(slot);

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

    /* Determine the partition to heap_insert the tuple into */
    if (mtstate->mt_partition_dispatch_info)
    {
        int         leaf_part_index;
        TupleConversionMap *map;

        /*
         * Away we go ... If we end up not finding a partition after all,
         * ExecFindPartition() does not return and errors out instead.
         * Otherwise, the returned value is to be used as an index into arrays
         * mt_partitions[] and mt_partition_tupconv_maps[] that will get us
         * the ResultRelInfo and TupleConversionMap for the partition,
         * respectively.
         */
        leaf_part_index = ExecFindPartition(resultRelInfo,
                                            mtstate->mt_partition_dispatch_info,
                                            slot,
                                            estate);
        Assert(leaf_part_index >= 0 &&
               leaf_part_index < mtstate->mt_num_partitions);

        /*
         * Save the old ResultRelInfo and switch to the one corresponding to
         * the selected partition.
         */
        saved_resultRelInfo = resultRelInfo;
        resultRelInfo = mtstate->mt_partitions + leaf_part_index;

        /* We do not yet have a way to insert into a foreign partition */
        if (resultRelInfo->ri_FdwRoutine)
            ereport(ERROR,
                    (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                     errmsg("cannot route inserted tuples to a foreign table")));

        /* For ExecInsertIndexTuples() to work on the partition's indexes */
        estate->es_result_relation_info = resultRelInfo;

        /*
         * We might need to convert from the parent rowtype to the partition
         * rowtype.
         */
        map = mtstate->mt_partition_tupconv_maps[leaf_part_index];
        if (map)
        {
            Relation    partrel = resultRelInfo->ri_RelationDesc;

            tuple = do_convert_tuple(tuple, map);

            /*
             * We must use the partition's tuple descriptor from this point
             * on, until we're finished dealing with the partition. Use the
             * dedicated slot for that.
             */
            slot = mtstate->mt_partition_tuple_slot;
            Assert(slot != NULL);
            ExecSetSlotDescriptor(slot, RelationGetDescr(partrel));
            ExecStoreTuple(tuple, slot, InvalidBuffer, true);
        }
    }

    resultRelationDesc = resultRelInfo->ri_RelationDesc;

    /*
     * If the result relation has OIDs, force the tuple's OID to zero so that
     * heap_insert will assign a fresh OID.  Usually the OID already will be
     * zero at this point, but there are corner cases where the plan tree can
     * return a tuple extracted literally from some table with the same
     * rowtype.
     *
     * XXX if we ever wanted to allow users to assign their own OIDs to new
     * rows, this'd be the place to do it.  For the moment, we make a point of
     * doing this before calling triggers, so that a user-supplied trigger
     * could hack the OID if desired.
     */
    if (resultRelationDesc->rd_rel->relhasoids)
        HeapTupleSetOid(tuple, InvalidOid);

    /*
     * 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)
    {
        slot = ExecBRInsertTriggers(estate, resultRelInfo, slot);

        if (slot == NULL)       /* "do nothing" */
            return NULL;

        /* trigger might have changed tuple */
        tuple = ExecMaterializeSlot(slot);
    }

    /* INSTEAD OF ROW INSERT Triggers */
    if (resultRelInfo->ri_TrigDesc &&
        resultRelInfo->ri_TrigDesc->trig_insert_instead_row)
    {
        slot = ExecIRInsertTriggers(estate, resultRelInfo, slot);

        if (slot == NULL)       /* "do nothing" */
            return NULL;

        /* trigger might have changed tuple */
        tuple = ExecMaterializeSlot(slot);

        newId = InvalidOid;
    }
    else if (resultRelInfo->ri_FdwRoutine)
    {
        /*
         * 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;

        /* FDW might have changed tuple */
        tuple = ExecMaterializeSlot(slot);

        /*
         * AFTER ROW Triggers or RETURNING expressions might reference the
         * tableoid column, so initialize t_tableOid before evaluating them.
         */
        tuple->t_tableOid = RelationGetRelid(resultRelationDesc);

        newId = InvalidOid;
    }
    else
    {
        /*
         * We always check the partition constraint, including when the tuple
         * got here via tuple-routing.  However we don't need to in the latter
         * case if no BR trigger is defined on the partition.  Note that a BR
         * trigger might modify the tuple such that the partition constraint
         * is no longer satisfied, so we need to check in that case.
         */
        bool        check_partition_constr =
        (resultRelInfo->ri_PartitionCheck != NIL);

        /*
         * Constraints might reference the tableoid column, so initialize
         * t_tableOid before evaluating them.
         */
        tuple->t_tableOid = RelationGetRelid(resultRelationDesc);

        /*
         * Check any RLS INSERT WITH CHECK policies
         *
         * 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_RLS_INSERT_CHECK,
                                 resultRelInfo, slot, estate);

        /*
         * No need though if the tuple has been routed, and a BR trigger
         * doesn't exist.
         */
        if (saved_resultRelInfo != NULL &&
            !(resultRelInfo->ri_TrigDesc &&
              resultRelInfo->ri_TrigDesc->trig_insert_before_row))
            check_partition_constr = false;

        /* Check the constraints of the tuple */
        if (resultRelationDesc->rd_att->constr || check_partition_constr)
            ExecConstraints(resultRelInfo, slot, estate);

        if (onconflict != ONCONFLICT_NONE && resultRelInfo->ri_NumIndices > 0)
        {
            /* Perform a speculative insertion. */
            uint32      specToken;
            ItemPointerData conflictTid;
            bool        specConflict;

            /*
             * 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))
                    {
                        InstrCountFiltered2(&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.
                     */
                    Assert(onconflict == ONCONFLICT_NOTHING);
                    ExecCheckTIDVisible(estate, resultRelInfo, &conflictTid);
                    InstrCountFiltered2(&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());
            HeapTupleHeaderSetSpeculativeToken(tuple->t_data, specToken);

            /* insert the tuple, with the speculative token */
            newId = heap_insert(resultRelationDesc, tuple,
                                estate->es_output_cid,
                                HEAP_INSERT_SPECULATIVE,
                                NULL);

            /* insert index entries for tuple */
            recheckIndexes = ExecInsertIndexTuples(slot, &(tuple->t_self),
                                                   estate, true, &specConflict,
                                                   arbiterIndexes);

            /* adjust the tuple's state accordingly */
            if (!specConflict)
                heap_finish_speculative(resultRelationDesc, tuple);
            else
                heap_abort_speculative(resultRelationDesc, tuple);

            /*
             * 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.
             *
             * Note: heap_insert returns the tid (location) of the new tuple
             * in the t_self field.
             */
            newId = heap_insert(resultRelationDesc, tuple,
                                estate->es_output_cid,
                                0, NULL);

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

    if (canSetTag)
    {
        (estate->es_processed)++;
        estate->es_lastoid = newId;
        setLastTid(&(tuple->t_self));
    }

    /* AFTER ROW INSERT Triggers */
    ExecARInsertTriggers(estate, resultRelInfo, tuple, recheckIndexes);

    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);

    if (saved_resultRelInfo)
        estate->es_result_relation_info = saved_resultRelInfo;

    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.
 *
 *      Returns RETURNING result if any, otherwise NULL.
 * ----------------------------------------------------------------
 */
static TupleTableSlot *
ExecDelete(ItemPointer tupleid,
           HeapTuple oldtuple,
           TupleTableSlot *planSlot,
           EPQState *epqstate,
           EState *estate,
           bool canSetTag)
{
    ResultRelInfo *resultRelInfo;
    Relation    resultRelationDesc;
    HTSU_Result result;
    HeapUpdateFailureData hufd;
    TupleTableSlot *slot = NULL;

    /*
     * 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);

        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)
    {
        HeapTuple   tuple;

        /*
         * delete from foreign table: let the FDW do it
         *
         * We offer the trigger tuple slot as a place to store RETURNING data,
         * although the FDW can return some other slot if it wants.  Set up
         * the slot's tupdesc so the FDW doesn't need to do that for itself.
         */
        slot = estate->es_trig_tuple_slot;
        if (slot->tts_tupleDescriptor != RelationGetDescr(resultRelationDesc))
            ExecSetSlotDescriptor(slot, RelationGetDescr(resultRelationDesc));

        slot = resultRelInfo->ri_FdwRoutine->ExecForeignDelete(estate,
                                                               resultRelInfo,
                                                               slot,
                                                               planSlot);

        if (slot == NULL)       /* "do nothing" */
            return NULL;

        /*
         * RETURNING expressions might reference the tableoid column, so
         * initialize t_tableOid before evaluating them.
         */
        if (slot->tts_isempty)
            ExecStoreAllNullTuple(slot);
        tuple = ExecMaterializeSlot(slot);
        tuple->t_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 = heap_delete(resultRelationDesc, tupleid,
                             estate->es_output_cid,
                             estate->es_crosscheck_snapshot,
                             true /* wait for commit */ ,
                             &hufd);
        switch (result)
        {
            case HeapTupleSelfUpdated:

                /*
                 * 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 (hufd.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 deleted by self; nothing to do */
                return NULL;

            case HeapTupleMayBeUpdated:
                break;

            case HeapTupleUpdated:
                if (IsolationUsesXactSnapshot())
                    ereport(ERROR,
                            (errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
                             errmsg("could not serialize access due to concurrent update")));
                if (!ItemPointerEquals(tupleid, &hufd.ctid))
                {
                    TupleTableSlot *epqslot;

                    epqslot = EvalPlanQual(estate,
                                           epqstate,
                                           resultRelationDesc,
                                           resultRelInfo->ri_RangeTableIndex,
                                           LockTupleExclusive,
                                           &hufd.ctid,
                                           hufd.xmax);
                    if (!TupIsNull(epqslot))
                    {
                        *tupleid = hufd.ctid;
                        goto ldelete;
                    }
                }
                /* tuple already deleted; nothing to do */
                return NULL;

            default:
                elog(ERROR, "unrecognized heap_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)++;

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

    /* Process RETURNING if present */
    if (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;
        HeapTupleData deltuple;
        Buffer      delbuffer;

        if (resultRelInfo->ri_FdwRoutine)
        {
            /* FDW must have provided a slot containing the deleted row */
            Assert(!TupIsNull(slot));
            delbuffer = InvalidBuffer;
        }
        else
        {
            slot = estate->es_trig_tuple_slot;
            if (oldtuple != NULL)
            {
                deltuple = *oldtuple;
                delbuffer = InvalidBuffer;
            }
            else
            {
                deltuple.t_self = *tupleid;
                if (!heap_fetch(resultRelationDesc, SnapshotAny,
                                &deltuple, &delbuffer, false, NULL))
                    elog(ERROR, "failed to fetch deleted tuple for DELETE RETURNING");
            }

            if (slot->tts_tupleDescriptor != RelationGetDescr(resultRelationDesc))
                ExecSetSlotDescriptor(slot, RelationGetDescr(resultRelationDesc));
            ExecStoreTuple(&deltuple, slot, InvalidBuffer, false);
        }

        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);
        if (BufferIsValid(delbuffer))
            ReleaseBuffer(delbuffer);

        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(ItemPointer tupleid,
           HeapTuple oldtuple,
           TupleTableSlot *slot,
           TupleTableSlot *planSlot,
           EPQState *epqstate,
           EState *estate,
           bool canSetTag)
{
    HeapTuple   tuple;
    ResultRelInfo *resultRelInfo;
    Relation    resultRelationDesc;
    HTSU_Result result;
    HeapUpdateFailureData hufd;
    List       *recheckIndexes = NIL;

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

    /*
     * get the heap tuple out of the tuple table slot, making sure we have a
     * writable copy
     */
    tuple = 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)
    {
        slot = ExecBRUpdateTriggers(estate, epqstate, resultRelInfo,
                                    tupleid, oldtuple, slot);

        if (slot == NULL)       /* "do nothing" */
            return NULL;

        /* trigger might have changed tuple */
        tuple = ExecMaterializeSlot(slot);
    }

    /* INSTEAD OF ROW UPDATE Triggers */
    if (resultRelInfo->ri_TrigDesc &&
        resultRelInfo->ri_TrigDesc->trig_update_instead_row)
    {
        slot = ExecIRUpdateTriggers(estate, resultRelInfo,
                                    oldtuple, slot);

        if (slot == NULL)       /* "do nothing" */
            return NULL;

        /* trigger might have changed tuple */
        tuple = ExecMaterializeSlot(slot);
    }
    else if (resultRelInfo->ri_FdwRoutine)
    {
        /*
         * 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;

        /* FDW might have changed tuple */
        tuple = ExecMaterializeSlot(slot);

        /*
         * AFTER ROW Triggers or RETURNING expressions might reference the
         * tableoid column, so initialize t_tableOid before evaluating them.
         */
        tuple->t_tableOid = RelationGetRelid(resultRelationDesc);
    }
    else
    {
        LockTupleMode lockmode;

        /*
         * Constraints might reference the tableoid column, so initialize
         * t_tableOid before evaluating them.
         */
        tuple->t_tableOid = RelationGetRelid(resultRelationDesc);

        /*
         * 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 heap_lock_tuple to lock the
         * correct tuple, so there's no need to do them again.)
         *
         * ExecWithCheckOptions() will skip any WCOs which are not of the kind
         * we are looking for at this point.
         */
lreplace:;
        if (resultRelInfo->ri_WithCheckOptions != NIL)
            ExecWithCheckOptions(WCO_RLS_UPDATE_CHECK,
                                 resultRelInfo, slot, estate);

        /*
         * Check the constraints of the tuple.  Note that we pass the same
         * slot for the orig_slot argument, because unlike ExecInsert(), no
         * tuple-routing is performed here, hence the slot remains unchanged.
         */
        if (resultRelationDesc->rd_att->constr || resultRelInfo->ri_PartitionCheck)
            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 = heap_update(resultRelationDesc, tupleid, tuple,
                             estate->es_output_cid,
                             estate->es_crosscheck_snapshot,
                             true /* wait for commit */ ,
                             &hufd, &lockmode);
        switch (result)
        {
            case HeapTupleSelfUpdated:

                /*
                 * 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 (hufd.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 HeapTupleMayBeUpdated:
                break;

            case HeapTupleUpdated:
                if (IsolationUsesXactSnapshot())
                    ereport(ERROR,
                            (errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
                             errmsg("could not serialize access due to concurrent update")));
                if (!ItemPointerEquals(tupleid, &hufd.ctid))
                {
                    TupleTableSlot *epqslot;

                    epqslot = EvalPlanQual(estate,
                                           epqstate,
                                           resultRelationDesc,
                                           resultRelInfo->ri_RangeTableIndex,
                                           lockmode,
                                           &hufd.ctid,
                                           hufd.xmax);
                    if (!TupIsNull(epqslot))
                    {
                        *tupleid = hufd.ctid;
                        slot = ExecFilterJunk(resultRelInfo->ri_junkFilter, epqslot);
                        tuple = ExecMaterializeSlot(slot);
                        goto lreplace;
                    }
                }
                /* tuple already deleted; nothing to do */
                return NULL;

            default:
                elog(ERROR, "unrecognized heap_update status: %u", result);
                return NULL;
        }

        /*
         * Note: instead of having to update the old index tuples associated
         * with the heap tuple, all we do is form and insert new index tuples.
         * This is because UPDATEs are actually DELETEs and INSERTs, and index
         * tuple deletion is done later by VACUUM (see notes in ExecDelete).
         * All we do here is insert new index tuples.  -cim 9/27/89
         */

        /*
         * insert index entries for tuple
         *
         * Note: heap_update returns the tid (location) of the new tuple in
         * the t_self field.
         *
         * If it's a HOT update, we mustn't insert new index entries.
         */
        if (resultRelInfo->ri_NumIndices > 0 && !HeapTupleIsHeapOnly(tuple))
            recheckIndexes = ExecInsertIndexTuples(slot, &(tuple->t_self),
                                                   estate, false, NULL, NIL);
    }

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

    /* AFTER ROW UPDATE Triggers */
    ExecARUpdateTriggers(estate, resultRelInfo, tupleid, oldtuple, tuple,
                         recheckIndexes);

    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 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_onConflictSetWhere;
    HeapTupleData tuple;
    HeapUpdateFailureData hufd;
    LockTupleMode lockmode;
    HTSU_Result test;
    Buffer      buffer;

    /* 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.
     */
    tuple.t_self = *conflictTid;
    test = heap_lock_tuple(relation, &tuple, estate->es_output_cid,
                           lockmode, LockWaitBlock, false, &buffer,
                           &hufd);
    switch (test)
    {
        case HeapTupleMayBeUpdated:
            /* success! */
            break;

        case HeapTupleInvisible:

            /*
             * 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()
             * HeapTupleSelfUpdated 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.
             */
            if (TransactionIdIsCurrentTransactionId(HeapTupleHeaderGetXmin(tuple.t_data)))
                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");

        case HeapTupleSelfUpdated:

            /*
             * 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");

        case HeapTupleUpdated:
            if (IsolationUsesXactSnapshot())
                ereport(ERROR,
                        (errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
                         errmsg("could not serialize access due to concurrent update")));

            /*
             * Tell caller to try again from the very start.
             *
             * It does not make sense to use the usual EvalPlanQual() style
             * loop here, as the new version of the row might not conflict
             * anymore, or the conflicting tuple has actually been deleted.
             */
            ReleaseBuffer(buffer);
            return false;

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

    /*
     * Success, the tuple is locked.
     *
     * Reset per-tuple memory context to free any expression evaluation
     * storage allocated in the previous cycle.
     */
    ResetExprContext(econtext);

    /*
     * 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.
     */
    ExecCheckHeapTupleVisible(estate, &tuple, buffer);

    /* Store target's existing tuple in the state's dedicated slot */
    ExecStoreTuple(&tuple, mtstate->mt_existing, buffer, false);

    /*
     * 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 = mtstate->mt_existing;
    econtext->ecxt_innertuple = excludedSlot;
    econtext->ecxt_outertuple = NULL;

    if (!ExecQual(onConflictSetWhere, econtext))
    {
        ReleaseBuffer(buffer);
        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,
                             mtstate->mt_existing,
                             mtstate->ps.state);
    }

    /* Project the new tuple version */
    ExecProject(resultRelInfo->ri_onConflictSetProj);

    /*
     * Note that it is possible that the target tuple has been modified in
     * this session, after the above heap_lock_tuple. 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(&tuple.t_self, NULL,
                            mtstate->mt_conflproj, planSlot,
                            &mtstate->mt_epqstate, mtstate->ps.state,
                            canSetTag);

    ReleaseBuffer(buffer);
    return true;
}


/*
 * Process BEFORE EACH STATEMENT triggers
 */
static void
fireBSTriggers(ModifyTableState *node)
{
    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 (node->mt_onconflict == 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;
    }
}

/*
 * Process AFTER EACH STATEMENT triggers
 */
static void
fireASTriggers(ModifyTableState *node)
{
    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:
            if (node->mt_onconflict == ONCONFLICT_UPDATE)
                ExecASUpdateTriggers(node->ps.state,
                                     resultRelInfo);
            ExecASInsertTriggers(node->ps.state, resultRelInfo);
            break;
        case CMD_UPDATE:
            ExecASUpdateTriggers(node->ps.state, resultRelInfo);
            break;
        case CMD_DELETE:
            ExecASDeleteTriggers(node->ps.state, resultRelInfo);
            break;
        default:
            elog(ERROR, "unknown operation");
            break;
    }
}


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

    /*
     * 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_epqTuple != 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);

        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]);
                continue;
            }
            else
                break;
        }

        /*
         * 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;

        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 an AFTER ROW 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:
                slot = ExecInsert(node, slot, planSlot,
                                  node->mt_arbiterindexes, node->mt_onconflict,
                                  estate, node->canSetTag);
                break;
            case CMD_UPDATE:
                slot = ExecUpdate(tupleid, oldtuple, slot, planSlot,
                                  &node->mt_epqstate, estate, node->canSetTag);
                break;
            case CMD_DELETE:
                slot = ExecDelete(tupleid, oldtuple, planSlot,
                                  &node->mt_epqstate, estate, node->canSetTag);
                break;
            default:
                elog(ERROR, "unknown operation");
                break;
        }

        /*
         * If we got a RETURNING result, return it to caller.  We'll continue
         * the work on next call.
         */
        if (slot)
        {
            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;
    TupleDesc   tupDesc;
    Plan       *subplan;
    ListCell   *l;
    int         i;
    Relation    rel;

    /* 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->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;

    /* 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;
    mtstate->mt_onconflict = node->onConflictAction;
    mtstate->mt_arbiterindexes = node->arbiterIndexes;

    /* 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; ExecContextForcesOids depends on that!
     */
    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->ri_RelationDesc, 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, mtstate->mt_onconflict != ONCONFLICT_NONE);

        /* Now init the plan for this result rel */
        estate->es_result_relation_info = resultRelInfo;
        mtstate->mt_plans[i] = ExecInitNode(subplan, estate, eflags);

        /* 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;

    /* The root table RT index is at the head of the partitioned_rels list */
    if (node->partitioned_rels)
    {
        Index       root_rti;
        Oid         root_oid;

        root_rti = linitial_int(node->partitioned_rels);
        root_oid = getrelid(root_rti, estate->es_range_table);
        rel = heap_open(root_oid, NoLock);  /* locked by InitPlan */
    }
    else
        rel = mtstate->resultRelInfo->ri_RelationDesc;

    /* Build state for INSERT tuple routing */
    if (operation == CMD_INSERT &&
        rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
    {
        PartitionDispatch *partition_dispatch_info;
        ResultRelInfo *partitions;
        TupleConversionMap **partition_tupconv_maps;
        TupleTableSlot *partition_tuple_slot;
        int         num_parted,
                    num_partitions;

        ExecSetupPartitionTupleRouting(rel,
                                       &partition_dispatch_info,
                                       &partitions,
                                       &partition_tupconv_maps,
                                       &partition_tuple_slot,
                                       &num_parted, &num_partitions);
        mtstate->mt_partition_dispatch_info = partition_dispatch_info;
        mtstate->mt_num_dispatch = num_parted;
        mtstate->mt_partitions = partitions;
        mtstate->mt_num_partitions = num_partitions;
        mtstate->mt_partition_tupconv_maps = partition_tupconv_maps;
        mtstate->mt_partition_tuple_slot = partition_tuple_slot;
    }

    /*
     * 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->mt_plans[i]);

            wcoExprs = lappend(wcoExprs, wcoExpr);
        }

        resultRelInfo->ri_WithCheckOptions = wcoList;
        resultRelInfo->ri_WithCheckOptionExprs = wcoExprs;
        resultRelInfo++;
        i++;
    }

    /*
     * Build WITH CHECK OPTION constraints for each leaf partition rel. Note
     * that we didn't build the withCheckOptionList for each partition within
     * the planner, but simple translation of the varattnos for each partition
     * will suffice.  This only occurs for the INSERT case; UPDATE/DELETE
     * cases are handled above.
     */
    if (node->withCheckOptionLists != NIL && mtstate->mt_num_partitions > 0)
    {
        List       *wcoList;
        PlanState  *plan;

        /*
         * In case of INSERT on partitioned tables, there is only one plan.
         * Likewise, there is only one WITH CHECK OPTIONS list, not one per
         * partition.  We make a copy of the WCO qual for each partition; note
         * that, if there are SubPlans in there, they all end up attached to
         * the one parent Plan node.
         */
        Assert(operation == CMD_INSERT &&
               list_length(node->withCheckOptionLists) == 1 &&
               mtstate->mt_nplans == 1);
        wcoList = linitial(node->withCheckOptionLists);
        plan = mtstate->mt_plans[0];
        resultRelInfo = mtstate->mt_partitions;
        for (i = 0; i < mtstate->mt_num_partitions; i++)
        {
            Relation    partrel = resultRelInfo->ri_RelationDesc;
            List       *mapped_wcoList;
            List       *wcoExprs = NIL;
            ListCell   *ll;

            /* varno = node->nominalRelation */
            mapped_wcoList = map_partition_varattnos(wcoList,
                                                     node->nominalRelation,
                                                     partrel, rel);
            foreach(ll, mapped_wcoList)
            {
                WithCheckOption *wco = castNode(WithCheckOption, lfirst(ll));
                ExprState  *wcoExpr = ExecInitQual(castNode(List, wco->qual),
                                                   plan);

                wcoExprs = lappend(wcoExprs, wcoExpr);
            }

            resultRelInfo->ri_WithCheckOptions = mapped_wcoList;
            resultRelInfo->ri_WithCheckOptionExprs = wcoExprs;
            resultRelInfo++;
        }
    }

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

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

        /* Set up a slot for the output of the RETURNING projection(s) */
        ExecInitResultTupleSlot(estate, &mtstate->ps);
        ExecAssignResultType(&mtstate->ps, tupDesc);
        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_projectReturning =
                ExecBuildProjectionInfo(rlist, econtext, slot, &mtstate->ps,
                                        resultRelInfo->ri_RelationDesc->rd_att);
            resultRelInfo++;
        }

        /*
         * Build a projection for each leaf partition rel.  Note that we
         * didn't build the returningList for each partition within the
         * planner, but simple translation of the varattnos for each partition
         * will suffice.  This only occurs for the INSERT case; UPDATE/DELETE
         * are handled above.
         */
        resultRelInfo = mtstate->mt_partitions;
        returningList = linitial(node->returningLists);
        for (i = 0; i < mtstate->mt_num_partitions; i++)
        {
            Relation    partrel = resultRelInfo->ri_RelationDesc;
            List       *rlist;

            /* varno = node->nominalRelation */
            rlist = map_partition_varattnos(returningList,
                                            node->nominalRelation,
                                            partrel, rel);
            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?).
         */
        tupDesc = ExecTypeFromTL(NIL, false);
        ExecInitResultTupleSlot(estate, &mtstate->ps);
        ExecAssignResultType(&mtstate->ps, tupDesc);

        mtstate->ps.ps_ExprContext = NULL;
    }

    /* Close the root partitioned rel if we opened it above. */
    if (rel != mtstate->resultRelInfo->ri_RelationDesc)
        heap_close(rel, NoLock);

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

        /* initialize slot for the existing tuple */
        mtstate->mt_existing = ExecInitExtraTupleSlot(mtstate->ps.state);
        ExecSetSlotDescriptor(mtstate->mt_existing,
                              resultRelInfo->ri_RelationDesc->rd_att);

        /* carried forward solely for the benefit of explain */
        mtstate->mt_excludedtlist = node->exclRelTlist;

        /* create target slot for UPDATE SET projection */
        tupDesc = ExecTypeFromTL((List *) node->onConflictSet,
                                 resultRelInfo->ri_RelationDesc->rd_rel->relhasoids);
        mtstate->mt_conflproj = ExecInitExtraTupleSlot(mtstate->ps.state);
        ExecSetSlotDescriptor(mtstate->mt_conflproj, tupDesc);

        /* build UPDATE SET projection state */
        resultRelInfo->ri_onConflictSetProj =
            ExecBuildProjectionInfo(node->onConflictSet, econtext,
                                    mtstate->mt_conflproj, &mtstate->ps,
                                    resultRelInfo->ri_RelationDesc->rd_att);

        /* build DO UPDATE WHERE clause expression */
        if (node->onConflictWhere)
        {
            ExprState  *qualexpr;

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

            resultRelInfo->ri_onConflictSetWhere = 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 a junk 'ctid' or 'wholerow'
     * attribute present --- no need to look first.
     *
     * 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;

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

                j = ExecInitJunkFilter(subplan->targetlist,
                                       resultRelInfo->ri_RelationDesc->rd_att->tdhasoid,
                                       ExecInitExtraTupleSlot(estate));

                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 an AFTER 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);
        }
    }

    /*
     * Set up a tuple table slot for use for trigger output tuples. In a plan
     * containing multiple ModifyTable nodes, all can share one such slot, so
     * we keep it in the estate.
     */
    if (estate->es_trig_tuple_slot == NULL)
        estate->es_trig_tuple_slot = ExecInitExtraTupleSlot(estate);

    /*
     * 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
     *
     * Remember node->mt_partition_dispatch_info[0] corresponds to the root
     * partitioned table, which we must not try to close, because it is the
     * main target table of the query that will be closed by ExecEndPlan().
     * Also, tupslot is NULL for the root partitioned table.
     */
    for (i = 1; i < node->mt_num_dispatch; i++)
    {
        PartitionDispatch pd = node->mt_partition_dispatch_info[i];

        heap_close(pd->reldesc, NoLock);
        ExecDropSingleTupleTableSlot(pd->tupslot);
    }
    for (i = 0; i < node->mt_num_partitions; i++)
    {
        ResultRelInfo *resultRelInfo = node->mt_partitions + i;

        ExecCloseIndices(resultRelInfo);
        heap_close(resultRelInfo->ri_RelationDesc, NoLock);
    }

    /* Release the standalone partition tuple descriptor, if any */
    if (node->mt_partition_tuple_slot)
        ExecDropSingleTupleTableSlot(node->mt_partition_tuple_slot);

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

    /*
     * clean out the tuple table
     */
    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");
}