nodeModifyTable.c

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/*-------------------------------------------------------------------------
 *
 * nodeModifyTable.c
 *    routines to handle ModifyTable nodes.
 *
 * Portions Copyright (c) 1996-2013, 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 "storage/bufmgr.h"
#include "utils/builtins.h"
#include "utils/memutils.h"
#include "utils/rel.h"
#include "utils/tqual.h"


/*
 * 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
 *
 * Returns a slot holding the result tuple
 */
static TupleTableSlot *
ExecProcessReturning(ProjectionInfo *projectReturning,
                     TupleTableSlot *tupleSlot,
                     TupleTableSlot *planSlot)
{
    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 */
    econtext->ecxt_scantuple = tupleSlot;
    econtext->ecxt_outertuple = planSlot;

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

/* ----------------------------------------------------------------
 *      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(TupleTableSlot *slot,
           TupleTableSlot *planSlot,
           EState *estate,
           bool canSetTag)
{
    HeapTuple   tuple;
    ResultRelInfo *resultRelInfo;
    Relation    resultRelationDesc;
    Oid         newId;
    List       *recheckIndexes = NIL;

    /*
     * 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;

    /*
     * 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 */
    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);

        newId = InvalidOid;
    }
    else
    {
        /*
         * Check the constraints of the tuple
         */
        if (resultRelationDesc->rd_att->constr)
            ExecConstraints(resultRelInfo, slot, estate);

        /*
         * insert the tuple
         *
         * 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);
    }

    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);

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

    return NULL;
}

/* ----------------------------------------------------------------
 *      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, both tupleid and oldtuple are NULL; the FDW has
 *      to figure out which row to delete using data from the planSlot.
 *
 *      Returns RETURNING result if any, otherwise NULL.
 * ----------------------------------------------------------------
 */
static TupleTableSlot *
ExecDelete(ItemPointer tupleid,
           HeapTupleHeader 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);

        if (!dodelete)          /* "do nothing" */
            return NULL;
    }

    /* INSTEAD OF ROW DELETE Triggers */
    if (resultRelInfo->ri_TrigDesc &&
        resultRelInfo->ri_TrigDesc->trig_delete_instead_row)
    {
        HeapTupleData tuple;
        bool        dodelete;

        Assert(oldtuple != NULL);
        tuple.t_data = oldtuple;
        tuple.t_len = HeapTupleHeaderGetDatumLength(oldtuple);
        ItemPointerSetInvalid(&(tuple.t_self));
        tuple.t_tableOid = InvalidOid;

        dodelete = ExecIRDeleteTriggers(estate, resultRelInfo, &tuple);

        if (!dodelete)          /* "do nothing" */
            return NULL;
    }
    else if (resultRelInfo->ri_FdwRoutine)
    {
        /*
         * 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;
    }
    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);

    /* 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.t_data = oldtuple;
                deltuple.t_len = HeapTupleHeaderGetDatumLength(oldtuple);
                ItemPointerSetInvalid(&(deltuple.t_self));
                deltuple.t_tableOid = InvalidOid;
                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->ri_projectReturning,
                                     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,
 *      both tupleid and oldtuple are NULL; the FDW has to figure out
 *      which row to update using data from the planSlot.
 *
 *      Returns RETURNING result if any, otherwise NULL.
 * ----------------------------------------------------------------
 */
static TupleTableSlot *
ExecUpdate(ItemPointer tupleid,
           HeapTupleHeader 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, 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)
    {
        HeapTupleData oldtup;

        Assert(oldtuple != NULL);
        oldtup.t_data = oldtuple;
        oldtup.t_len = HeapTupleHeaderGetDatumLength(oldtuple);
        ItemPointerSetInvalid(&(oldtup.t_self));
        oldtup.t_tableOid = InvalidOid;

        slot = ExecIRUpdateTriggers(estate, resultRelInfo,
                                    &oldtup, 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);
    }
    else
    {
        LockTupleMode   lockmode;

        /*
         * Check the constraints of the tuple
         *
         * If we generate a new candidate tuple after EvalPlanQual testing, we
         * must loop back here and recheck 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.)
         */
lreplace:;
        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 = 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);
    }

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

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

    list_free(recheckIndexes);

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

    return NULL;
}


/*
 * Process BEFORE EACH STATEMENT triggers
 */
static void
fireBSTriggers(ModifyTableState *node)
{
    switch (node->operation)
    {
        case CMD_INSERT:
            ExecBSInsertTriggers(node->ps.state, node->resultRelInfo);
            break;
        case CMD_UPDATE:
            ExecBSUpdateTriggers(node->ps.state, node->resultRelInfo);
            break;
        case CMD_DELETE:
            ExecBSDeleteTriggers(node->ps.state, node->resultRelInfo);
            break;
        default:
            elog(ERROR, "unknown operation");
            break;
    }
}

/*
 * Process AFTER EACH STATEMENT triggers
 */
static void
fireASTriggers(ModifyTableState *node)
{
    switch (node->operation)
    {
        case CMD_INSERT:
            ExecASInsertTriggers(node->ps.state, node->resultRelInfo);
            break;
        case CMD_UPDATE:
            ExecASUpdateTriggers(node->ps.state, node->resultRelInfo);
            break;
        case CMD_DELETE:
            ExecASDeleteTriggers(node->ps.state, node->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;
    HeapTupleHeader oldtuple = NULL;

    /*
     * 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;
        }

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

        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)
                {
                    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;
                }
                else if (relkind == RELKIND_FOREIGN_TABLE)
                {
                    /* do nothing; FDW must fetch any junk attrs it wants */
                }
                else
                {
                    datum = ExecGetJunkAttribute(slot,
                                                 junkfilter->jf_junkAttNo,
                                                 &isNull);
                    /* shouldn't ever get a null result... */
                    if (isNull)
                        elog(ERROR, "wholerow is NULL");

                    oldtuple = DatumGetHeapTupleHeader(datum);
                }
            }

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

        switch (operation)
        {
            case CMD_INSERT:
                slot = ExecInsert(slot, planSlot, 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;

    /* 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.targetlist = NIL;       /* not actually used */

    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_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; ExecContextForcesOids depends on that!
     */
    saved_resultRelInfo = estate->es_result_relation_info;

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

        /*
         * 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);

        /* 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_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;

    /*
     * 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.
         */
        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 */
        econtext = CreateExprContext(estate);
        mtstate->ps.ps_ExprContext = econtext;

        /*
         * Build a projection for each result rel.
         */
        resultRelInfo = mtstate->resultRelInfo;
        foreach(l, node->returningLists)
        {
            List       *rlist = (List *) lfirst(l);
            List       *rliststate;

            rliststate = (List *) ExecInitExpr((Expr *) rlist, &mtstate->ps);
            resultRelInfo->ri_projectReturning =
                ExecBuildProjectionInfo(rliststate, econtext, slot,
                                     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;
    }

    /*
     * 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 = (PlanRowMark *) lfirst(l);
        ExecRowMark *erm;

        Assert(IsA(rc, PlanRowMark));

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

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

        /* 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)
                    {
                        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)
                    {
                        /* FDW must fetch any junk attrs it wants */
                    }
                    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_FdwRoutine != NULL &&
            resultRelInfo->ri_FdwRoutine->EndForeignModify != NULL)
            resultRelInfo->ri_FdwRoutine->EndForeignModify(node->ps.state,
                                                           resultRelInfo);
    }

    /*
     * 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");
}