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Sourcecode: postgresql-8.4 version File versions

execMain.c

/*-------------------------------------------------------------------------
 *
 * execMain.c
 *      top level executor interface routines
 *
 * INTERFACE ROUTINES
 *    ExecutorStart()
 *    ExecutorRun()
 *    ExecutorEnd()
 *
 *    The old ExecutorMain() has been replaced by ExecutorStart(),
 *    ExecutorRun() and ExecutorEnd()
 *
 *    These three procedures are the external interfaces to the executor.
 *    In each case, the query descriptor is required as an argument.
 *
 *    ExecutorStart() must be called at the beginning of execution of any
 *    query plan and ExecutorEnd() should always be called at the end of
 *    execution of a plan.
 *
 *    ExecutorRun accepts direction and count arguments that specify whether
 *    the plan is to be executed forwards, backwards, and for how many tuples.
 *
 * Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *      $PostgreSQL: pgsql/src/backend/executor/execMain.c,v 1.326 2009/06/11 20:46:11 tgl Exp $
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "access/heapam.h"
#include "access/reloptions.h"
#include "access/sysattr.h"
#include "access/transam.h"
#include "access/xact.h"
#include "catalog/heap.h"
#include "catalog/namespace.h"
#include "catalog/toasting.h"
#include "commands/tablespace.h"
#include "commands/trigger.h"
#include "executor/execdebug.h"
#include "executor/instrument.h"
#include "executor/nodeSubplan.h"
#include "miscadmin.h"
#include "nodes/nodeFuncs.h"
#include "optimizer/clauses.h"
#include "parser/parse_clause.h"
#include "parser/parsetree.h"
#include "storage/bufmgr.h"
#include "storage/lmgr.h"
#include "storage/smgr.h"
#include "utils/acl.h"
#include "utils/builtins.h"
#include "utils/lsyscache.h"
#include "utils/memutils.h"
#include "utils/snapmgr.h"
#include "utils/tqual.h"


/* Hooks for plugins to get control in ExecutorStart/Run/End() */
ExecutorStart_hook_type ExecutorStart_hook = NULL;
ExecutorRun_hook_type ExecutorRun_hook = NULL;
ExecutorEnd_hook_type ExecutorEnd_hook = NULL;

typedef struct evalPlanQual
{
      Index       rti;
      EState         *estate;
      PlanState  *planstate;
      struct evalPlanQual *next;    /* stack of active PlanQual plans */
      struct evalPlanQual *free;    /* list of free PlanQual plans */
} evalPlanQual;

/* decls for local routines only used within this module */
static void InitPlan(QueryDesc *queryDesc, int eflags);
static void ExecCheckPlanOutput(Relation resultRel, List *targetList);
static void ExecEndPlan(PlanState *planstate, EState *estate);
static void ExecutePlan(EState *estate, PlanState *planstate,
                  CmdType operation,
                  long numberTuples,
                  ScanDirection direction,
                  DestReceiver *dest);
static void ExecSelect(TupleTableSlot *slot,
               DestReceiver *dest, EState *estate);
static void ExecInsert(TupleTableSlot *slot, ItemPointer tupleid,
               TupleTableSlot *planSlot,
               DestReceiver *dest, EState *estate);
static void ExecDelete(ItemPointer tupleid,
               TupleTableSlot *planSlot,
               DestReceiver *dest, EState *estate);
static void ExecUpdate(TupleTableSlot *slot, ItemPointer tupleid,
               TupleTableSlot *planSlot,
               DestReceiver *dest, EState *estate);
static void ExecProcessReturning(ProjectionInfo *projectReturning,
                               TupleTableSlot *tupleSlot,
                               TupleTableSlot *planSlot,
                               DestReceiver *dest);
static TupleTableSlot *EvalPlanQualNext(EState *estate);
static void EndEvalPlanQual(EState *estate);
static void ExecCheckRTPerms(List *rangeTable);
static void ExecCheckRTEPerms(RangeTblEntry *rte);
static void ExecCheckXactReadOnly(PlannedStmt *plannedstmt);
static void EvalPlanQualStart(evalPlanQual *epq, EState *estate,
                          evalPlanQual *priorepq);
static void EvalPlanQualStop(evalPlanQual *epq);
static void OpenIntoRel(QueryDesc *queryDesc);
static void CloseIntoRel(QueryDesc *queryDesc);
static void intorel_startup(DestReceiver *self, int operation, TupleDesc typeinfo);
static void intorel_receive(TupleTableSlot *slot, DestReceiver *self);
static void intorel_shutdown(DestReceiver *self);
static void intorel_destroy(DestReceiver *self);

/* end of local decls */


/* ----------------------------------------------------------------
 *          ExecutorStart
 *
 *          This routine must be called at the beginning of any execution of any
 *          query plan
 *
 * Takes a QueryDesc previously created by CreateQueryDesc (it's not real
 * clear why we bother to separate the two functions, but...).    The tupDesc
 * field of the QueryDesc is filled in to describe the tuples that will be
 * returned, and the internal fields (estate and planstate) are set up.
 *
 * eflags contains flag bits as described in executor.h.
 *
 * NB: the CurrentMemoryContext when this is called will become the parent
 * of the per-query context used for this Executor invocation.
 *
 * We provide a function hook variable that lets loadable plugins
 * get control when ExecutorStart is called.  Such a plugin would
 * normally call standard_ExecutorStart().
 *
 * ----------------------------------------------------------------
 */
void
ExecutorStart(QueryDesc *queryDesc, int eflags)
{
      if (ExecutorStart_hook)
            (*ExecutorStart_hook) (queryDesc, eflags);
      else
            standard_ExecutorStart(queryDesc, eflags);
}

void
standard_ExecutorStart(QueryDesc *queryDesc, int eflags)
{
      EState         *estate;
      MemoryContext oldcontext;

      /* sanity checks: queryDesc must not be started already */
      Assert(queryDesc != NULL);
      Assert(queryDesc->estate == NULL);

      /*
       * If the transaction is read-only, we need to check if any writes are
       * planned to non-temporary tables.  EXPLAIN is considered read-only.
       */
      if (XactReadOnly && !(eflags & EXEC_FLAG_EXPLAIN_ONLY))
            ExecCheckXactReadOnly(queryDesc->plannedstmt);

      /*
       * Build EState, switch into per-query memory context for startup.
       */
      estate = CreateExecutorState();
      queryDesc->estate = estate;

      oldcontext = MemoryContextSwitchTo(estate->es_query_cxt);

      /*
       * Fill in parameters, if any, from queryDesc
       */
      estate->es_param_list_info = queryDesc->params;

      if (queryDesc->plannedstmt->nParamExec > 0)
            estate->es_param_exec_vals = (ParamExecData *)
                  palloc0(queryDesc->plannedstmt->nParamExec * sizeof(ParamExecData));

      /*
       * If non-read-only query, set the command ID to mark output tuples with
       */
      switch (queryDesc->operation)
      {
            case CMD_SELECT:
                  /* SELECT INTO and SELECT FOR UPDATE/SHARE need to mark tuples */
                  if (queryDesc->plannedstmt->intoClause != NULL ||
                        queryDesc->plannedstmt->rowMarks != NIL)
                        estate->es_output_cid = GetCurrentCommandId(true);
                  break;

            case CMD_INSERT:
            case CMD_DELETE:
            case CMD_UPDATE:
                  estate->es_output_cid = GetCurrentCommandId(true);
                  break;

            default:
                  elog(ERROR, "unrecognized operation code: %d",
                         (int) queryDesc->operation);
                  break;
      }

      /*
       * Copy other important information into the EState
       */
      estate->es_snapshot = RegisterSnapshot(queryDesc->snapshot);
      estate->es_crosscheck_snapshot = RegisterSnapshot(queryDesc->crosscheck_snapshot);
      estate->es_instrument = queryDesc->doInstrument;

      /*
       * Initialize the plan state tree
       */
      InitPlan(queryDesc, eflags);

      MemoryContextSwitchTo(oldcontext);
}

/* ----------------------------------------------------------------
 *          ExecutorRun
 *
 *          This is the main routine of the executor module. It accepts
 *          the query descriptor from the traffic cop and executes the
 *          query plan.
 *
 *          ExecutorStart must have been called already.
 *
 *          If direction is NoMovementScanDirection then nothing is done
 *          except to start up/shut down the destination.  Otherwise,
 *          we retrieve up to 'count' tuples in the specified direction.
 *
 *          Note: count = 0 is interpreted as no portal limit, i.e., run to
 *          completion.
 *
 *          There is no return value, but output tuples (if any) are sent to
 *          the destination receiver specified in the QueryDesc; and the number
 *          of tuples processed at the top level can be found in
 *          estate->es_processed.
 *
 *          We provide a function hook variable that lets loadable plugins
 *          get control when ExecutorRun is called.  Such a plugin would
 *          normally call standard_ExecutorRun().
 *
 * ----------------------------------------------------------------
 */
void
ExecutorRun(QueryDesc *queryDesc,
                  ScanDirection direction, long count)
{
      if (ExecutorRun_hook)
            (*ExecutorRun_hook) (queryDesc, direction, count);
      else
            standard_ExecutorRun(queryDesc, direction, count);
}

void
standard_ExecutorRun(QueryDesc *queryDesc,
                               ScanDirection direction, long count)
{
      EState         *estate;
      CmdType           operation;
      DestReceiver *dest;
      bool        sendTuples;
      MemoryContext oldcontext;

      /* sanity checks */
      Assert(queryDesc != NULL);

      estate = queryDesc->estate;

      Assert(estate != NULL);

      /*
       * Switch into per-query memory context
       */
      oldcontext = MemoryContextSwitchTo(estate->es_query_cxt);

      /* Allow instrumentation of ExecutorRun overall runtime */
      if (queryDesc->totaltime)
            InstrStartNode(queryDesc->totaltime);

      /*
       * extract information from the query descriptor and the query feature.
       */
      operation = queryDesc->operation;
      dest = queryDesc->dest;

      /*
       * startup tuple receiver, if we will be emitting tuples
       */
      estate->es_processed = 0;
      estate->es_lastoid = InvalidOid;

      sendTuples = (operation == CMD_SELECT ||
                          queryDesc->plannedstmt->returningLists);

      if (sendTuples)
            (*dest->rStartup) (dest, operation, queryDesc->tupDesc);

      /*
       * run plan
       */
      if (!ScanDirectionIsNoMovement(direction))
            ExecutePlan(estate,
                              queryDesc->planstate,
                              operation,
                              count,
                              direction,
                              dest);

      /*
       * shutdown tuple receiver, if we started it
       */
      if (sendTuples)
            (*dest->rShutdown) (dest);

      if (queryDesc->totaltime)
            InstrStopNode(queryDesc->totaltime, estate->es_processed);

      MemoryContextSwitchTo(oldcontext);
}

/* ----------------------------------------------------------------
 *          ExecutorEnd
 *
 *          This routine must be called at the end of execution of any
 *          query plan
 *
 *          We provide a function hook variable that lets loadable plugins
 *          get control when ExecutorEnd is called.  Such a plugin would
 *          normally call standard_ExecutorEnd().
 *
 * ----------------------------------------------------------------
 */
void
ExecutorEnd(QueryDesc *queryDesc)
{
      if (ExecutorEnd_hook)
            (*ExecutorEnd_hook) (queryDesc);
      else
            standard_ExecutorEnd(queryDesc);
}

void
standard_ExecutorEnd(QueryDesc *queryDesc)
{
      EState         *estate;
      MemoryContext oldcontext;

      /* sanity checks */
      Assert(queryDesc != NULL);

      estate = queryDesc->estate;

      Assert(estate != NULL);

      /*
       * Switch into per-query memory context to run ExecEndPlan
       */
      oldcontext = MemoryContextSwitchTo(estate->es_query_cxt);

      ExecEndPlan(queryDesc->planstate, estate);

      /*
       * Close the SELECT INTO relation if any
       */
      if (estate->es_select_into)
            CloseIntoRel(queryDesc);

      /* do away with our snapshots */
      UnregisterSnapshot(estate->es_snapshot);
      UnregisterSnapshot(estate->es_crosscheck_snapshot);

      /*
       * Must switch out of context before destroying it
       */
      MemoryContextSwitchTo(oldcontext);

      /*
       * Release EState and per-query memory context.  This should release
       * everything the executor has allocated.
       */
      FreeExecutorState(estate);

      /* Reset queryDesc fields that no longer point to anything */
      queryDesc->tupDesc = NULL;
      queryDesc->estate = NULL;
      queryDesc->planstate = NULL;
      queryDesc->totaltime = NULL;
}

/* ----------------------------------------------------------------
 *          ExecutorRewind
 *
 *          This routine may be called on an open queryDesc to rewind it
 *          to the start.
 * ----------------------------------------------------------------
 */
void
ExecutorRewind(QueryDesc *queryDesc)
{
      EState         *estate;
      MemoryContext oldcontext;

      /* sanity checks */
      Assert(queryDesc != NULL);

      estate = queryDesc->estate;

      Assert(estate != NULL);

      /* It's probably not sensible to rescan updating queries */
      Assert(queryDesc->operation == CMD_SELECT);

      /*
       * Switch into per-query memory context
       */
      oldcontext = MemoryContextSwitchTo(estate->es_query_cxt);

      /*
       * rescan plan
       */
      ExecReScan(queryDesc->planstate, NULL);

      MemoryContextSwitchTo(oldcontext);
}


/*
 * ExecCheckRTPerms
 *          Check access permissions for all relations listed in a range table.
 */
static void
ExecCheckRTPerms(List *rangeTable)
{
      ListCell   *l;

      foreach(l, rangeTable)
      {
            ExecCheckRTEPerms((RangeTblEntry *) lfirst(l));
      }
}

/*
 * ExecCheckRTEPerms
 *          Check access permissions for a single RTE.
 */
static void
ExecCheckRTEPerms(RangeTblEntry *rte)
{
      AclMode           requiredPerms;
      AclMode           relPerms;
      AclMode           remainingPerms;
      Oid               relOid;
      Oid               userid;
      Bitmapset  *tmpset;
      int               col;

      /*
       * Only plain-relation RTEs need to be checked here.  Function RTEs are
       * checked by init_fcache when the function is prepared for execution.
       * Join, subquery, and special RTEs need no checks.
       */
      if (rte->rtekind != RTE_RELATION)
            return;

      /*
       * No work if requiredPerms is empty.
       */
      requiredPerms = rte->requiredPerms;
      if (requiredPerms == 0)
            return;

      relOid = rte->relid;

      /*
       * userid to check as: current user unless we have a setuid indication.
       *
       * Note: GetUserId() is presently fast enough that there's no harm in
       * calling it separately for each RTE.    If that stops being true, we could
       * call it once in ExecCheckRTPerms and pass the userid down from there.
       * But for now, no need for the extra clutter.
       */
      userid = rte->checkAsUser ? rte->checkAsUser : GetUserId();

      /*
       * We must have *all* the requiredPerms bits, but some of the bits can be
       * satisfied from column-level rather than relation-level permissions.
       * First, remove any bits that are satisfied by relation permissions.
       */
      relPerms = pg_class_aclmask(relOid, userid, requiredPerms, ACLMASK_ALL);
      remainingPerms = requiredPerms & ~relPerms;
      if (remainingPerms != 0)
      {
            /*
             * If we lack any permissions that exist only as relation permissions,
             * we can fail straight away.
             */
            if (remainingPerms & ~(ACL_SELECT | ACL_INSERT | ACL_UPDATE))
                  aclcheck_error(ACLCHECK_NO_PRIV, ACL_KIND_CLASS,
                                       get_rel_name(relOid));

            /*
             * Check to see if we have the needed privileges at column level.
             *
             * Note: failures just report a table-level error; it would be nicer
             * to report a column-level error if we have some but not all of the
             * column privileges.
             */
            if (remainingPerms & ACL_SELECT)
            {
                  /*
                   * When the query doesn't explicitly reference any columns (for
                   * example, SELECT COUNT(*) FROM table), allow the query if we
                   * have SELECT on any column of the rel, as per SQL spec.
                   */
                  if (bms_is_empty(rte->selectedCols))
                  {
                        if (pg_attribute_aclcheck_all(relOid, userid, ACL_SELECT,
                                                                    ACLMASK_ANY) != ACLCHECK_OK)
                              aclcheck_error(ACLCHECK_NO_PRIV, ACL_KIND_CLASS,
                                                   get_rel_name(relOid));
                  }

                  tmpset = bms_copy(rte->selectedCols);
                  while ((col = bms_first_member(tmpset)) >= 0)
                  {
                        /* remove the column number offset */
                        col += FirstLowInvalidHeapAttributeNumber;
                        if (col == InvalidAttrNumber)
                        {
                              /* Whole-row reference, must have priv on all cols */
                              if (pg_attribute_aclcheck_all(relOid, userid, ACL_SELECT,
                                                                          ACLMASK_ALL) != ACLCHECK_OK)
                                    aclcheck_error(ACLCHECK_NO_PRIV, ACL_KIND_CLASS,
                                                         get_rel_name(relOid));
                        }
                        else
                        {
                              if (pg_attribute_aclcheck(relOid, col, userid, ACL_SELECT)
                                    != ACLCHECK_OK)
                                    aclcheck_error(ACLCHECK_NO_PRIV, ACL_KIND_CLASS,
                                                         get_rel_name(relOid));
                        }
                  }
                  bms_free(tmpset);
            }

            /*
             * Basically the same for the mod columns, with either INSERT or
             * UPDATE privilege as specified by remainingPerms.
             */
            remainingPerms &= ~ACL_SELECT;
            if (remainingPerms != 0)
            {
                  /*
                   * When the query doesn't explicitly change any columns, allow the
                   * query if we have permission on any column of the rel.  This is
                   * to handle SELECT FOR UPDATE as well as possible corner cases in
                   * INSERT and UPDATE.
                   */
                  if (bms_is_empty(rte->modifiedCols))
                  {
                        if (pg_attribute_aclcheck_all(relOid, userid, remainingPerms,
                                                                    ACLMASK_ANY) != ACLCHECK_OK)
                              aclcheck_error(ACLCHECK_NO_PRIV, ACL_KIND_CLASS,
                                                   get_rel_name(relOid));
                  }

                  tmpset = bms_copy(rte->modifiedCols);
                  while ((col = bms_first_member(tmpset)) >= 0)
                  {
                        /* remove the column number offset */
                        col += FirstLowInvalidHeapAttributeNumber;
                        if (col == InvalidAttrNumber)
                        {
                              /* whole-row reference can't happen here */
                              elog(ERROR, "whole-row update is not implemented");
                        }
                        else
                        {
                              if (pg_attribute_aclcheck(relOid, col, userid, remainingPerms)
                                    != ACLCHECK_OK)
                                    aclcheck_error(ACLCHECK_NO_PRIV, ACL_KIND_CLASS,
                                                         get_rel_name(relOid));
                        }
                  }
                  bms_free(tmpset);
            }
      }
}

/*
 * Check that the query does not imply any writes to non-temp tables.
 */
static void
ExecCheckXactReadOnly(PlannedStmt *plannedstmt)
{
      ListCell   *l;

      /*
       * CREATE TABLE AS or SELECT INTO?
       *
       * XXX should we allow this if the destination is temp?
       */
      if (plannedstmt->intoClause != NULL)
            goto fail;

      /* Fail if write permissions are requested on any non-temp table */
      foreach(l, plannedstmt->rtable)
      {
            RangeTblEntry *rte = (RangeTblEntry *) lfirst(l);

            if (rte->rtekind != RTE_RELATION)
                  continue;

            if ((rte->requiredPerms & (~ACL_SELECT)) == 0)
                  continue;

            if (isTempNamespace(get_rel_namespace(rte->relid)))
                  continue;

            goto fail;
      }

      return;

fail:
      ereport(ERROR,
                  (errcode(ERRCODE_READ_ONLY_SQL_TRANSACTION),
                   errmsg("transaction is read-only")));
}


/* ----------------------------------------------------------------
 *          InitPlan
 *
 *          Initializes the query plan: open files, allocate storage
 *          and start up the rule manager
 * ----------------------------------------------------------------
 */
static void
InitPlan(QueryDesc *queryDesc, int eflags)
{
      CmdType           operation = queryDesc->operation;
      PlannedStmt *plannedstmt = queryDesc->plannedstmt;
      Plan     *plan = plannedstmt->planTree;
      List     *rangeTable = plannedstmt->rtable;
      EState         *estate = queryDesc->estate;
      PlanState  *planstate;
      TupleDesc   tupType;
      ListCell   *l;
      int               i;

      /*
       * Do permissions checks
       */
      ExecCheckRTPerms(rangeTable);

      /*
       * initialize the node's execution state
       */
      estate->es_range_table = rangeTable;

      /*
       * initialize result relation stuff
       */
      if (plannedstmt->resultRelations)
      {
            List     *resultRelations = plannedstmt->resultRelations;
            int               numResultRelations = list_length(resultRelations);
            ResultRelInfo *resultRelInfos;
            ResultRelInfo *resultRelInfo;

            resultRelInfos = (ResultRelInfo *)
                  palloc(numResultRelations * sizeof(ResultRelInfo));
            resultRelInfo = resultRelInfos;
            foreach(l, resultRelations)
            {
                  Index       resultRelationIndex = lfirst_int(l);
                  Oid               resultRelationOid;
                  Relation    resultRelation;

                  resultRelationOid = getrelid(resultRelationIndex, rangeTable);
                  resultRelation = heap_open(resultRelationOid, RowExclusiveLock);
                  InitResultRelInfo(resultRelInfo,
                                            resultRelation,
                                            resultRelationIndex,
                                            operation,
                                            estate->es_instrument);
                  resultRelInfo++;
            }
            estate->es_result_relations = resultRelInfos;
            estate->es_num_result_relations = numResultRelations;
            /* Initialize to first or only result rel */
            estate->es_result_relation_info = resultRelInfos;
      }
      else
      {
            /*
             * if no result relation, then set state appropriately
             */
            estate->es_result_relations = NULL;
            estate->es_num_result_relations = 0;
            estate->es_result_relation_info = NULL;
      }

      /*
       * Detect whether we're doing SELECT INTO.  If so, set the es_into_oids
       * flag appropriately so that the plan tree will be initialized with the
       * correct tuple descriptors.  (Other SELECT INTO stuff comes later.)
       */
      estate->es_select_into = false;
      if (operation == CMD_SELECT && plannedstmt->intoClause != NULL)
      {
            estate->es_select_into = true;
            estate->es_into_oids = interpretOidsOption(plannedstmt->intoClause->options);
      }

      /*
       * Have to lock relations selected FOR UPDATE/FOR SHARE before we
       * initialize the plan tree, else we'd be doing a lock upgrade. While we
       * are at it, build the ExecRowMark list.
       */
      estate->es_rowMarks = NIL;
      foreach(l, plannedstmt->rowMarks)
      {
            RowMarkClause *rc = (RowMarkClause *) lfirst(l);
            Oid               relid;
            Relation    relation;
            ExecRowMark *erm;

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

            relid = getrelid(rc->rti, rangeTable);
            relation = heap_open(relid, RowShareLock);
            erm = (ExecRowMark *) palloc(sizeof(ExecRowMark));
            erm->relation = relation;
            erm->rti = rc->rti;
            erm->prti = rc->prti;
            erm->forUpdate = rc->forUpdate;
            erm->noWait = rc->noWait;
            /* We'll locate the junk attrs below */
            erm->ctidAttNo = InvalidAttrNumber;
            erm->toidAttNo = InvalidAttrNumber;
            ItemPointerSetInvalid(&(erm->curCtid));
            estate->es_rowMarks = lappend(estate->es_rowMarks, erm);
      }

      /*
       * Initialize the executor "tuple" table.  We need slots for all the plan
       * nodes, plus possibly output slots for the junkfilter(s). At this point
       * we aren't sure if we need junkfilters, so just add slots for them
       * unconditionally.  Also, if it's not a SELECT, set up a slot for use for
       * trigger output tuples.  Also, one for RETURNING-list evaluation.
       */
      {
            int               nSlots;

            /* Slots for the main plan tree */
            nSlots = ExecCountSlotsNode(plan);
            /* Add slots for subplans and initplans */
            foreach(l, plannedstmt->subplans)
            {
                  Plan     *subplan = (Plan *) lfirst(l);

                  nSlots += ExecCountSlotsNode(subplan);
            }
            /* Add slots for junkfilter(s) */
            if (plannedstmt->resultRelations != NIL)
                  nSlots += list_length(plannedstmt->resultRelations);
            else
                  nSlots += 1;
            if (operation != CMD_SELECT)
                  nSlots++;               /* for es_trig_tuple_slot */
            if (plannedstmt->returningLists)
                  nSlots++;               /* for RETURNING projection */

            estate->es_tupleTable = ExecCreateTupleTable(nSlots);

            if (operation != CMD_SELECT)
                  estate->es_trig_tuple_slot =
                        ExecAllocTableSlot(estate->es_tupleTable);
      }

      /* mark EvalPlanQual not active */
      estate->es_plannedstmt = plannedstmt;
      estate->es_evalPlanQual = NULL;
      estate->es_evTupleNull = NULL;
      estate->es_evTuple = NULL;
      estate->es_useEvalPlan = false;

      /*
       * Initialize private state information for each SubPlan.  We must do this
       * before running ExecInitNode on the main query tree, since
       * ExecInitSubPlan expects to be able to find these entries.
       */
      Assert(estate->es_subplanstates == NIL);
      i = 1;                                    /* subplan indices count from 1 */
      foreach(l, plannedstmt->subplans)
      {
            Plan     *subplan = (Plan *) lfirst(l);
            PlanState  *subplanstate;
            int               sp_eflags;

            /*
             * A subplan will never need to do BACKWARD scan nor MARK/RESTORE. If
             * it is a parameterless subplan (not initplan), we suggest that it be
             * prepared to handle REWIND efficiently; otherwise there is no need.
             */
            sp_eflags = eflags & EXEC_FLAG_EXPLAIN_ONLY;
            if (bms_is_member(i, plannedstmt->rewindPlanIDs))
                  sp_eflags |= EXEC_FLAG_REWIND;

            subplanstate = ExecInitNode(subplan, estate, sp_eflags);

            estate->es_subplanstates = lappend(estate->es_subplanstates,
                                                               subplanstate);

            i++;
      }

      /*
       * Initialize the private state information for all the nodes in the query
       * tree.  This opens files, allocates storage and leaves us ready to start
       * processing tuples.
       */
      planstate = ExecInitNode(plan, estate, eflags);

      /*
       * Get the tuple descriptor describing the type of tuples to return. (this
       * is especially important if we are creating a relation with "SELECT
       * INTO")
       */
      tupType = ExecGetResultType(planstate);

      /*
       * Initialize the junk filter if needed.  SELECT and 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' attribute
       * present --- no need to look first.
       *
       * 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;
            ListCell   *tlist;

            switch (operation)
            {
                  case CMD_SELECT:
                  case CMD_INSERT:
                        foreach(tlist, plan->targetlist)
                        {
                              TargetEntry *tle = (TargetEntry *) lfirst(tlist);

                              if (tle->resjunk)
                              {
                                    junk_filter_needed = true;
                                    break;
                              }
                        }
                        break;
                  case CMD_UPDATE:
                  case CMD_DELETE:
                        junk_filter_needed = true;
                        break;
                  default:
                        break;
            }

            if (junk_filter_needed)
            {
                  /*
                   * If there are multiple result relations, each one needs its own
                   * junk filter.  Note this is only possible for UPDATE/DELETE, so
                   * we can't be fooled by some needing a filter and some not.
                   */
                  if (list_length(plannedstmt->resultRelations) > 1)
                  {
                        PlanState **appendplans;
                        int               as_nplans;
                        ResultRelInfo *resultRelInfo;

                        /* Top plan had better be an Append here. */
                        Assert(IsA(plan, Append));
                        Assert(((Append *) plan)->isTarget);
                        Assert(IsA(planstate, AppendState));
                        appendplans = ((AppendState *) planstate)->appendplans;
                        as_nplans = ((AppendState *) planstate)->as_nplans;
                        Assert(as_nplans == estate->es_num_result_relations);
                        resultRelInfo = estate->es_result_relations;
                        for (i = 0; i < as_nplans; i++)
                        {
                              PlanState  *subplan = appendplans[i];
                              JunkFilter *j;

                              if (operation == CMD_UPDATE)
                                    ExecCheckPlanOutput(resultRelInfo->ri_RelationDesc,
                                                                  subplan->plan->targetlist);

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

                              /*
                               * Since it must be UPDATE/DELETE, there had better be a
                               * "ctid" junk attribute in the tlist ... but ctid could
                               * be at a different resno for each result relation. We
                               * look up the ctid resnos now and save them in the
                               * junkfilters.
                               */
                              j->jf_junkAttNo = ExecFindJunkAttribute(j, "ctid");
                              if (!AttributeNumberIsValid(j->jf_junkAttNo))
                                    elog(ERROR, "could not find junk ctid column");
                              resultRelInfo->ri_junkFilter = j;
                              resultRelInfo++;
                        }

                        /*
                         * Set active junkfilter too; at this point ExecInitAppend has
                         * already selected an active result relation...
                         */
                        estate->es_junkFilter =
                              estate->es_result_relation_info->ri_junkFilter;

                        /*
                         * We currently can't support rowmarks in this case, because
                         * the associated junk CTIDs might have different resnos in
                         * different subplans.
                         */
                        if (estate->es_rowMarks)
                              ereport(ERROR,
                                          (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                                           errmsg("SELECT FOR UPDATE/SHARE is not supported within a query with multiple result relations")));
                  }
                  else
                  {
                        /* Normal case with just one JunkFilter */
                        JunkFilter *j;

                        if (operation == CMD_INSERT || operation == CMD_UPDATE)
                              ExecCheckPlanOutput(estate->es_result_relation_info->ri_RelationDesc,
                                                            planstate->plan->targetlist);

                        j = ExecInitJunkFilter(planstate->plan->targetlist,
                                                         tupType->tdhasoid,
                                                  ExecAllocTableSlot(estate->es_tupleTable));
                        estate->es_junkFilter = j;
                        if (estate->es_result_relation_info)
                              estate->es_result_relation_info->ri_junkFilter = j;

                        if (operation == CMD_SELECT)
                        {
                              /* For SELECT, want to return the cleaned tuple type */
                              tupType = j->jf_cleanTupType;
                        }
                        else if (operation == CMD_UPDATE || operation == CMD_DELETE)
                        {
                              /* For UPDATE/DELETE, find the ctid junk attr now */
                              j->jf_junkAttNo = ExecFindJunkAttribute(j, "ctid");
                              if (!AttributeNumberIsValid(j->jf_junkAttNo))
                                    elog(ERROR, "could not find junk ctid column");
                        }

                        /* For SELECT FOR UPDATE/SHARE, find the junk attrs now */
                        foreach(l, estate->es_rowMarks)
                        {
                              ExecRowMark *erm = (ExecRowMark *) lfirst(l);
                              char        resname[32];

                              /* always need the ctid */
                              snprintf(resname, sizeof(resname), "ctid%u",
                                           erm->prti);
                              erm->ctidAttNo = ExecFindJunkAttribute(j, resname);
                              if (!AttributeNumberIsValid(erm->ctidAttNo))
                                    elog(ERROR, "could not find junk \"%s\" column",
                                           resname);
                              /* if child relation, need tableoid too */
                              if (erm->rti != erm->prti)
                              {
                                    snprintf(resname, sizeof(resname), "tableoid%u",
                                                 erm->prti);
                                    erm->toidAttNo = ExecFindJunkAttribute(j, resname);
                                    if (!AttributeNumberIsValid(erm->toidAttNo))
                                          elog(ERROR, "could not find junk \"%s\" column",
                                                 resname);
                              }
                        }
                  }
            }
            else
            {
                  if (operation == CMD_INSERT)
                        ExecCheckPlanOutput(estate->es_result_relation_info->ri_RelationDesc,
                                                      planstate->plan->targetlist);

                  estate->es_junkFilter = NULL;
                  if (estate->es_rowMarks)
                        elog(ERROR, "SELECT FOR UPDATE/SHARE, but no junk columns");
            }
      }

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

            /*
             * We set QueryDesc.tupDesc to be the RETURNING rowtype in this case.
             * We assume all the sublists will generate the same output tupdesc.
             */
            tupType = ExecTypeFromTL((List *) linitial(plannedstmt->returningLists),
                                                 false);

            /* Set up a slot for the output of the RETURNING projection(s) */
            slot = ExecAllocTableSlot(estate->es_tupleTable);
            ExecSetSlotDescriptor(slot, tupType);
            /* Need an econtext too */
            econtext = CreateExprContext(estate);

            /*
             * Build a projection for each result rel.      Note that any SubPlans in
             * the RETURNING lists get attached to the topmost plan node.
             */
            Assert(list_length(plannedstmt->returningLists) == estate->es_num_result_relations);
            resultRelInfo = estate->es_result_relations;
            foreach(l, plannedstmt->returningLists)
            {
                  List     *rlist = (List *) lfirst(l);
                  List     *rliststate;

                  rliststate = (List *) ExecInitExpr((Expr *) rlist, planstate);
                  resultRelInfo->ri_projectReturning =
                        ExecBuildProjectionInfo(rliststate, econtext, slot,
                                                       resultRelInfo->ri_RelationDesc->rd_att);
                  resultRelInfo++;
            }
      }

      queryDesc->tupDesc = tupType;
      queryDesc->planstate = planstate;

      /*
       * If doing SELECT INTO, initialize the "into" relation.  We must wait
       * till now so we have the "clean" result tuple type to create the new
       * table from.
       *
       * If EXPLAIN, skip creating the "into" relation.
       */
      if (estate->es_select_into && !(eflags & EXEC_FLAG_EXPLAIN_ONLY))
            OpenIntoRel(queryDesc);
}

/*
 * Initialize ResultRelInfo data for one result relation
 */
void
InitResultRelInfo(ResultRelInfo *resultRelInfo,
                          Relation resultRelationDesc,
                          Index resultRelationIndex,
                          CmdType operation,
                          bool doInstrument)
{
      /*
       * Check valid relkind ... parser and/or planner should have noticed this
       * already, but let's make sure.
       */
      switch (resultRelationDesc->rd_rel->relkind)
      {
            case RELKIND_RELATION:
                  /* OK */
                  break;
            case RELKIND_SEQUENCE:
                  ereport(ERROR,
                              (errcode(ERRCODE_WRONG_OBJECT_TYPE),
                               errmsg("cannot change sequence \"%s\"",
                                          RelationGetRelationName(resultRelationDesc))));
                  break;
            case RELKIND_TOASTVALUE:
                  ereport(ERROR,
                              (errcode(ERRCODE_WRONG_OBJECT_TYPE),
                               errmsg("cannot change TOAST relation \"%s\"",
                                          RelationGetRelationName(resultRelationDesc))));
                  break;
            case RELKIND_VIEW:
                  ereport(ERROR,
                              (errcode(ERRCODE_WRONG_OBJECT_TYPE),
                               errmsg("cannot change view \"%s\"",
                                          RelationGetRelationName(resultRelationDesc))));
                  break;
            default:
                  ereport(ERROR,
                              (errcode(ERRCODE_WRONG_OBJECT_TYPE),
                               errmsg("cannot change relation \"%s\"",
                                          RelationGetRelationName(resultRelationDesc))));
                  break;
      }

      /* OK, fill in the node */
      MemSet(resultRelInfo, 0, sizeof(ResultRelInfo));
      resultRelInfo->type = T_ResultRelInfo;
      resultRelInfo->ri_RangeTableIndex = resultRelationIndex;
      resultRelInfo->ri_RelationDesc = resultRelationDesc;
      resultRelInfo->ri_NumIndices = 0;
      resultRelInfo->ri_IndexRelationDescs = NULL;
      resultRelInfo->ri_IndexRelationInfo = NULL;
      /* make a copy so as not to depend on relcache info not changing... */
      resultRelInfo->ri_TrigDesc = CopyTriggerDesc(resultRelationDesc->trigdesc);
      if (resultRelInfo->ri_TrigDesc)
      {
            int               n = resultRelInfo->ri_TrigDesc->numtriggers;

            resultRelInfo->ri_TrigFunctions = (FmgrInfo *)
                  palloc0(n * sizeof(FmgrInfo));
            if (doInstrument)
                  resultRelInfo->ri_TrigInstrument = InstrAlloc(n);
            else
                  resultRelInfo->ri_TrigInstrument = NULL;
      }
      else
      {
            resultRelInfo->ri_TrigFunctions = NULL;
            resultRelInfo->ri_TrigInstrument = NULL;
      }
      resultRelInfo->ri_ConstraintExprs = NULL;
      resultRelInfo->ri_junkFilter = NULL;
      resultRelInfo->ri_projectReturning = NULL;

      /*
       * 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.
       */
      if (resultRelationDesc->rd_rel->relhasindex &&
            operation != CMD_DELETE)
            ExecOpenIndices(resultRelInfo);
}

/*
 * 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.")));
}

/*
 *          ExecGetTriggerResultRel
 *
 * Get a ResultRelInfo for a trigger target relation.  Most of the time,
 * triggers are fired on one of the result relations of the query, and so
 * we can just return a member of the es_result_relations array.  (Note: in
 * self-join situations there might be multiple members with the same OID;
 * if so it doesn't matter which one we pick.)  However, it is sometimes
 * necessary to fire triggers on other relations; this happens mainly when an
 * RI update trigger queues additional triggers on other relations, which will
 * be processed in the context of the outer query.    For efficiency's sake,
 * we want to have a ResultRelInfo for those triggers too; that can avoid
 * repeated re-opening of the relation.  (It also provides a way for EXPLAIN
 * ANALYZE to report the runtimes of such triggers.)  So we make additional
 * ResultRelInfo's as needed, and save them in es_trig_target_relations.
 */
ResultRelInfo *
ExecGetTriggerResultRel(EState *estate, Oid relid)
{
      ResultRelInfo *rInfo;
      int               nr;
      ListCell   *l;
      Relation    rel;
      MemoryContext oldcontext;

      /* First, search through the query result relations */
      rInfo = estate->es_result_relations;
      nr = estate->es_num_result_relations;
      while (nr > 0)
      {
            if (RelationGetRelid(rInfo->ri_RelationDesc) == relid)
                  return rInfo;
            rInfo++;
            nr--;
      }
      /* Nope, but maybe we already made an extra ResultRelInfo for it */
      foreach(l, estate->es_trig_target_relations)
      {
            rInfo = (ResultRelInfo *) lfirst(l);
            if (RelationGetRelid(rInfo->ri_RelationDesc) == relid)
                  return rInfo;
      }
      /* Nope, so we need a new one */

      /*
       * Open the target relation's relcache entry.  We assume that an
       * appropriate lock is still held by the backend from whenever the trigger
       * event got queued, so we need take no new lock here.
       */
      rel = heap_open(relid, NoLock);

      /*
       * Make the new entry in the right context.  Currently, we don't need any
       * index information in ResultRelInfos used only for triggers, so tell
       * InitResultRelInfo it's a DELETE.
       */
      oldcontext = MemoryContextSwitchTo(estate->es_query_cxt);
      rInfo = makeNode(ResultRelInfo);
      InitResultRelInfo(rInfo,
                                rel,
                                0,        /* dummy rangetable index */
                                CMD_DELETE,
                                estate->es_instrument);
      estate->es_trig_target_relations =
            lappend(estate->es_trig_target_relations, rInfo);
      MemoryContextSwitchTo(oldcontext);

      return rInfo;
}

/*
 *          ExecContextForcesOids
 *
 * This is pretty grotty: when doing INSERT, UPDATE, or SELECT INTO,
 * we need to ensure that result tuples have space for an OID iff they are
 * going to be stored into a relation that has OIDs.  In other contexts
 * we are free to choose whether to leave space for OIDs in result tuples
 * (we generally don't want to, but we do if a physical-tlist optimization
 * is possible).  This routine checks the plan context and returns TRUE if the
 * choice is forced, FALSE if the choice is not forced.  In the TRUE case,
 * *hasoids is set to the required value.
 *
 * One reason this is ugly is that all plan nodes in the plan tree will emit
 * tuples with space for an OID, though we really only need the topmost node
 * to do so.  However, node types like Sort don't project new tuples but just
 * return their inputs, and in those cases the requirement propagates down
 * to the input node.  Eventually we might make this code smart enough to
 * recognize how far down the requirement really goes, but for now we just
 * make all plan nodes do the same thing if the top level forces the choice.
 *
 * We assume that estate->es_result_relation_info is already set up to
 * describe the target relation.  Note that in an UPDATE that spans an
 * inheritance tree, some of the target relations may have OIDs and some not.
 * We have to make the decisions on a per-relation basis as we initialize
 * each of the child plans of the topmost Append plan.
 *
 * SELECT INTO is even uglier, because we don't have the INTO relation's
 * descriptor available when this code runs; we have to look aside at a
 * flag set by InitPlan().
 */
bool
ExecContextForcesOids(PlanState *planstate, bool *hasoids)
{
      if (planstate->state->es_select_into)
      {
            *hasoids = planstate->state->es_into_oids;
            return true;
      }
      else
      {
            ResultRelInfo *ri = planstate->state->es_result_relation_info;

            if (ri != NULL)
            {
                  Relation    rel = ri->ri_RelationDesc;

                  if (rel != NULL)
                  {
                        *hasoids = rel->rd_rel->relhasoids;
                        return true;
                  }
            }
      }

      return false;
}

/* ----------------------------------------------------------------
 *          ExecEndPlan
 *
 *          Cleans up the query plan -- closes files and frees up storage
 *
 * NOTE: we are no longer very worried about freeing storage per se
 * in this code; FreeExecutorState should be guaranteed to release all
 * memory that needs to be released.  What we are worried about doing
 * is closing relations and dropping buffer pins.  Thus, for example,
 * tuple tables must be cleared or dropped to ensure pins are released.
 * ----------------------------------------------------------------
 */
static void
ExecEndPlan(PlanState *planstate, EState *estate)
{
      ResultRelInfo *resultRelInfo;
      int               i;
      ListCell   *l;

      /*
       * shut down any PlanQual processing we were doing
       */
      if (estate->es_evalPlanQual != NULL)
            EndEvalPlanQual(estate);

      /*
       * shut down the node-type-specific query processing
       */
      ExecEndNode(planstate);

      /*
       * for subplans too
       */
      foreach(l, estate->es_subplanstates)
      {
            PlanState  *subplanstate = (PlanState *) lfirst(l);

            ExecEndNode(subplanstate);
      }

      /*
       * destroy the executor "tuple" table.
       */
      ExecDropTupleTable(estate->es_tupleTable, true);
      estate->es_tupleTable = NULL;

      /*
       * close the result relation(s) if any, but hold locks until xact commit.
       */
      resultRelInfo = estate->es_result_relations;
      for (i = estate->es_num_result_relations; i > 0; i--)
      {
            /* Close indices and then the relation itself */
            ExecCloseIndices(resultRelInfo);
            heap_close(resultRelInfo->ri_RelationDesc, NoLock);
            resultRelInfo++;
      }

      /*
       * likewise close any trigger target relations
       */
      foreach(l, estate->es_trig_target_relations)
      {
            resultRelInfo = (ResultRelInfo *) lfirst(l);
            /* Close indices and then the relation itself */
            ExecCloseIndices(resultRelInfo);
            heap_close(resultRelInfo->ri_RelationDesc, NoLock);
      }

      /*
       * close any relations selected FOR UPDATE/FOR SHARE, again keeping locks
       */
      foreach(l, estate->es_rowMarks)
      {
            ExecRowMark *erm = lfirst(l);

            heap_close(erm->relation, NoLock);
      }
}

/* ----------------------------------------------------------------
 *          ExecutePlan
 *
 *          Processes the query plan until we have processed 'numberTuples' tuples,
 *          moving in the specified direction.
 *
 *          Runs to completion if numberTuples is 0
 *
 * Note: the ctid attribute is a 'junk' attribute that is removed before the
 * user can see it
 * ----------------------------------------------------------------
 */
static void
ExecutePlan(EState *estate,
                  PlanState *planstate,
                  CmdType operation,
                  long numberTuples,
                  ScanDirection direction,
                  DestReceiver *dest)
{
      JunkFilter *junkfilter;
      TupleTableSlot *planSlot;
      TupleTableSlot *slot;
      ItemPointer tupleid = NULL;
      ItemPointerData tuple_ctid;
      long        current_tuple_count;

      /*
       * initialize local variables
       */
      current_tuple_count = 0;

      /*
       * Set the direction.
       */
      estate->es_direction = direction;

      /*
       * Process BEFORE EACH STATEMENT triggers
       */
      switch (operation)
      {
            case CMD_UPDATE:
                  ExecBSUpdateTriggers(estate, estate->es_result_relation_info);
                  break;
            case CMD_DELETE:
                  ExecBSDeleteTriggers(estate, estate->es_result_relation_info);
                  break;
            case CMD_INSERT:
                  ExecBSInsertTriggers(estate, estate->es_result_relation_info);
                  break;
            default:
                  /* do nothing */
                  break;
      }

      /*
       * Loop until we've processed the proper number of tuples from the plan.
       */
      for (;;)
      {
            /* Reset the per-output-tuple exprcontext */
            ResetPerTupleExprContext(estate);

            /*
             * Execute the plan and obtain a tuple
             */
lnext:      ;
            if (estate->es_useEvalPlan)
            {
                  planSlot = EvalPlanQualNext(estate);
                  if (TupIsNull(planSlot))
                        planSlot = ExecProcNode(planstate);
            }
            else
                  planSlot = ExecProcNode(planstate);

            /*
             * if the tuple is null, then we assume there is nothing more to
             * process so we just end the loop...
             */
            if (TupIsNull(planSlot))
                  break;
            slot = planSlot;

            /*
             * If we have a junk filter, then project a new tuple with the junk
             * removed.
             *
             * Store this new "clean" tuple in the junkfilter's resultSlot.
             * (Formerly, we stored it back over the "dirty" tuple, which is WRONG
             * because that tuple slot has the wrong descriptor.)
             *
             * But first, extract all the junk information we need.
             */
            if ((junkfilter = estate->es_junkFilter) != NULL)
            {
                  /*
                   * Process any FOR UPDATE or FOR SHARE locking requested.
                   */
                  if (estate->es_rowMarks != NIL)
                  {
                        ListCell   *l;

            lmark:      ;
                        foreach(l, estate->es_rowMarks)
                        {
                              ExecRowMark *erm = lfirst(l);
                              Datum       datum;
                              bool        isNull;
                              HeapTupleData tuple;
                              Buffer            buffer;
                              ItemPointerData update_ctid;
                              TransactionId update_xmax;
                              TupleTableSlot *newSlot;
                              LockTupleMode lockmode;
                              HTSU_Result test;

                              /* if child rel, must check whether it produced this row */
                              if (erm->rti != erm->prti)
                              {
                                    Oid               tableoid;

                                    datum = ExecGetJunkAttribute(slot,
                                                                               erm->toidAttNo,
                                                                               &isNull);
                                    /* shouldn't ever get a null result... */
                                    if (isNull)
                                          elog(ERROR, "tableoid is NULL");
                                    tableoid = DatumGetObjectId(datum);

                                    if (tableoid != RelationGetRelid(erm->relation))
                                    {
                                          /* this child is inactive right now */
                                          ItemPointerSetInvalid(&(erm->curCtid));
                                          continue;
                                    }
                              }

                              /* okay, fetch the tuple by ctid */
                              datum = ExecGetJunkAttribute(slot,
                                                                         erm->ctidAttNo,
                                                                         &isNull);
                              /* shouldn't ever get a null result... */
                              if (isNull)
                                    elog(ERROR, "ctid is NULL");
                              tuple.t_self = *((ItemPointer) DatumGetPointer(datum));

                              if (erm->forUpdate)
                                    lockmode = LockTupleExclusive;
                              else
                                    lockmode = LockTupleShared;

                              test = heap_lock_tuple(erm->relation, &tuple, &buffer,
                                                               &update_ctid, &update_xmax,
                                                               estate->es_output_cid,
                                                               lockmode, erm->noWait);
                              ReleaseBuffer(buffer);
                              switch (test)
                              {
                                    case HeapTupleSelfUpdated:
                                          /* treat it as deleted; do not process */
                                          goto lnext;

                                    case HeapTupleMayBeUpdated:
                                          break;

                                    case HeapTupleUpdated:
                                          if (IsXactIsoLevelSerializable)
                                                ereport(ERROR,
                                                 (errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
                                                  errmsg("could not serialize access due to concurrent update")));
                                          if (!ItemPointerEquals(&update_ctid,
                                                                           &tuple.t_self))
                                          {
                                                /* updated, so look at updated version */
                                                newSlot = EvalPlanQual(estate,
                                                                                 erm->rti,
                                                                                 &update_ctid,
                                                                                 update_xmax);
                                                if (!TupIsNull(newSlot))
                                                {
                                                      slot = planSlot = newSlot;
                                                      estate->es_useEvalPlan = true;
                                                      goto lmark;
                                                }
                                          }

                                          /*
                                           * if tuple was deleted or PlanQual failed for
                                           * updated tuple - we must not return this tuple!
                                           */
                                          goto lnext;

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

                              /* Remember tuple TID for WHERE CURRENT OF */
                              erm->curCtid = tuple.t_self;
                        }
                  }

                  /*
                   * extract the 'ctid' junk attribute.
                   */
                  if (operation == CMD_UPDATE || operation == CMD_DELETE)
                  {
                        Datum       datum;
                        bool        isNull;

                        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;  /* make sure we don't free the ctid!! */
                        tupleid = &tuple_ctid;
                  }

                  /*
                   * Create a new "clean" tuple with all junk attributes removed. We
                   * don't need to do this for DELETE, however (there will in fact
                   * be no non-junk attributes in a DELETE!)
                   */
                  if (operation != CMD_DELETE)
                        slot = ExecFilterJunk(junkfilter, slot);
            }

            /*
             * now that we have a tuple, do the appropriate thing with it.. either
             * send it to the output destination, add it to a relation someplace,
             * delete it from a relation, or modify some of its attributes.
             */
            switch (operation)
            {
                  case CMD_SELECT:
                        ExecSelect(slot, dest, estate);
                        break;

                  case CMD_INSERT:
                        ExecInsert(slot, tupleid, planSlot, dest, estate);
                        break;

                  case CMD_DELETE:
                        ExecDelete(tupleid, planSlot, dest, estate);
                        break;

                  case CMD_UPDATE:
                        ExecUpdate(slot, tupleid, planSlot, dest, estate);
                        break;

                  default:
                        elog(ERROR, "unrecognized operation code: %d",
                               (int) operation);
                        break;
            }

            /*
             * check our tuple count.. if we've processed the proper number then
             * quit, else loop again and process more tuples.  Zero numberTuples
             * means no limit.
             */
            current_tuple_count++;
            if (numberTuples && numberTuples == current_tuple_count)
                  break;
      }

      /*
       * Process AFTER EACH STATEMENT triggers
       */
      switch (operation)
      {
            case CMD_UPDATE:
                  ExecASUpdateTriggers(estate, estate->es_result_relation_info);
                  break;
            case CMD_DELETE:
                  ExecASDeleteTriggers(estate, estate->es_result_relation_info);
                  break;
            case CMD_INSERT:
                  ExecASInsertTriggers(estate, estate->es_result_relation_info);
                  break;
            default:
                  /* do nothing */
                  break;
      }
}

/* ----------------------------------------------------------------
 *          ExecSelect
 *
 *          SELECTs are easy.. we just pass the tuple to the appropriate
 *          output function.
 * ----------------------------------------------------------------
 */
static void
ExecSelect(TupleTableSlot *slot,
               DestReceiver *dest,
               EState *estate)
{
      (*dest->receiveSlot) (slot, dest);
      IncrRetrieved();
      (estate->es_processed)++;
}

/* ----------------------------------------------------------------
 *          ExecInsert
 *
 *          INSERTs are trickier.. we have to insert the tuple into
 *          the base relation and insert appropriate tuples into the
 *          index relations.
 * ----------------------------------------------------------------
 */
static void
ExecInsert(TupleTableSlot *slot,
               ItemPointer tupleid,
               TupleTableSlot *planSlot,
               DestReceiver *dest,
               EState *estate)
{
      HeapTuple   tuple;
      ResultRelInfo *resultRelInfo;
      Relation    resultRelationDesc;
      Oid               newId;

      /*
       * 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->n_before_row[TRIGGER_EVENT_INSERT] > 0)
      {
            HeapTuple   newtuple;

            newtuple = ExecBRInsertTriggers(estate, resultRelInfo, tuple);

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

            if (newtuple != tuple)  /* modified by Trigger(s) */
            {
                  /*
                   * Put the modified tuple into a slot for convenience of routines
                   * below.  We assume the tuple was allocated in per-tuple memory
                   * context, and therefore will go away by itself. The tuple table
                   * slot should not try to clear it.
                   */
                  TupleTableSlot *newslot = estate->es_trig_tuple_slot;

                  if (newslot->tts_tupleDescriptor != slot->tts_tupleDescriptor)
                        ExecSetSlotDescriptor(newslot, slot->tts_tupleDescriptor);
                  ExecStoreTuple(newtuple, newslot, InvalidBuffer, false);
                  slot = newslot;
                  tuple = newtuple;
            }
      }

      /*
       * 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);

      IncrAppended();
      (estate->es_processed)++;
      estate->es_lastoid = newId;
      setLastTid(&(tuple->t_self));

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

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

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

/* ----------------------------------------------------------------
 *          ExecDelete
 *
 *          DELETE is like UPDATE, except that we delete the tuple and no
 *          index modifications are needed
 * ----------------------------------------------------------------
 */
static void
ExecDelete(ItemPointer tupleid,
               TupleTableSlot *planSlot,
               DestReceiver *dest,
               EState *estate)
{
      ResultRelInfo *resultRelInfo;
      Relation    resultRelationDesc;
      HTSU_Result result;
      ItemPointerData update_ctid;
      TransactionId update_xmax;

      /*
       * 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->n_before_row[TRIGGER_EVENT_DELETE] > 0)
      {
            bool        dodelete;

            dodelete = ExecBRDeleteTriggers(estate, resultRelInfo, tupleid);

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

      /*
       * 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 serializable transactions.
       */
ldelete:;
      result = heap_delete(resultRelationDesc, tupleid,
                                     &update_ctid, &update_xmax,
                                     estate->es_output_cid,
                                     estate->es_crosscheck_snapshot,
                                     true /* wait for commit */ );
      switch (result)
      {
            case HeapTupleSelfUpdated:
                  /* already deleted by self; nothing to do */
                  return;

            case HeapTupleMayBeUpdated:
                  break;

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

                        epqslot = EvalPlanQual(estate,
                                                         resultRelInfo->ri_RangeTableIndex,
                                                         &update_ctid,
                                                         update_xmax);
                        if (!TupIsNull(epqslot))
                        {
                              *tupleid = update_ctid;
                              goto ldelete;
                        }
                  }
                  /* tuple already deleted; nothing to do */
                  return;

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

      IncrDeleted();
      (estate->es_processed)++;

      /*
       * 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.
       */

      /* 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 *slot = estate->es_trig_tuple_slot;
            HeapTupleData deltuple;
            Buffer            delbuffer;

            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);

            ExecProcessReturning(resultRelInfo->ri_projectReturning,
                                           slot, planSlot, dest);

            ExecClearTuple(slot);
            ReleaseBuffer(delbuffer);
      }
}

/* ----------------------------------------------------------------
 *          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..
 * ----------------------------------------------------------------
 */
static void
ExecUpdate(TupleTableSlot *slot,
               ItemPointer tupleid,
               TupleTableSlot *planSlot,
               DestReceiver *dest,
               EState *estate)
{
      HeapTuple   tuple;
      ResultRelInfo *resultRelInfo;
      Relation    resultRelationDesc;
      HTSU_Result result;
      ItemPointerData update_ctid;
      TransactionId update_xmax;

      /*
       * 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->n_before_row[TRIGGER_EVENT_UPDATE] > 0)
      {
            HeapTuple   newtuple;

            newtuple = ExecBRUpdateTriggers(estate, resultRelInfo,
                                                            tupleid, tuple);

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

            if (newtuple != tuple)  /* modified by Trigger(s) */
            {
                  /*
                   * Put the modified tuple into a slot for convenience of routines
                   * below.  We assume the tuple was allocated in per-tuple memory
                   * context, and therefore will go away by itself. The tuple table
                   * slot should not try to clear it.
                   */
                  TupleTableSlot *newslot = estate->es_trig_tuple_slot;

                  if (newslot->tts_tupleDescriptor != slot->tts_tupleDescriptor)
                        ExecSetSlotDescriptor(newslot, slot->tts_tupleDescriptor);
                  ExecStoreTuple(newtuple, newslot, InvalidBuffer, false);
                  slot = newslot;
                  tuple = newtuple;
            }
      }

      /*
       * 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 serializable transactions.
       */
      result = heap_update(resultRelationDesc, tupleid, tuple,
                                     &update_ctid, &update_xmax,
                                     estate->es_output_cid,
                                     estate->es_crosscheck_snapshot,
                                     true /* wait for commit */ );
      switch (result)
      {
            case HeapTupleSelfUpdated:
                  /* already deleted by self; nothing to do */
                  return;

            case HeapTupleMayBeUpdated:
                  break;

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

                        epqslot = EvalPlanQual(estate,
                                                         resultRelInfo->ri_RangeTableIndex,
                                                         &update_ctid,
                                                         update_xmax);
                        if (!TupIsNull(epqslot))
                        {
                              *tupleid = update_ctid;
                              slot = ExecFilterJunk(estate->es_junkFilter, epqslot);
                              tuple = ExecMaterializeSlot(slot);
                              goto lreplace;
                        }
                  }
                  /* tuple already deleted; nothing to do */
                  return;

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

      IncrReplaced();
      (estate->es_processed)++;

      /*
       * 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))
            ExecInsertIndexTuples(slot, &(tuple->t_self), estate, false);

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

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

/*
 * ExecRelCheck --- check that tuple meets constraints for result relation
 */
static const char *
ExecRelCheck(ResultRelInfo *resultRelInfo,
                   TupleTableSlot *slot, EState *estate)
{
      Relation    rel = resultRelInfo->ri_RelationDesc;
      int               ncheck = rel->rd_att->constr->num_check;
      ConstrCheck *check = rel->rd_att->constr->check;
      ExprContext *econtext;
      MemoryContext oldContext;
      List     *qual;
      int               i;

      /*
       * If first time through for this result relation, build expression
       * nodetrees for rel's constraint expressions.  Keep them in the per-query
       * memory context so they'll survive throughout the query.
       */
      if (resultRelInfo->ri_ConstraintExprs == NULL)
      {
            oldContext = MemoryContextSwitchTo(estate->es_query_cxt);
            resultRelInfo->ri_ConstraintExprs =
                  (List **) palloc(ncheck * sizeof(List *));
            for (i = 0; i < ncheck; i++)
            {
                  /* ExecQual wants implicit-AND form */
                  qual = make_ands_implicit(stringToNode(check[i].ccbin));
                  resultRelInfo->ri_ConstraintExprs[i] = (List *)
                        ExecPrepareExpr((Expr *) qual, estate);
            }
            MemoryContextSwitchTo(oldContext);
      }

      /*
       * We will use the EState's per-tuple context for evaluating constraint
       * expressions (creating it if it's not already there).
       */
      econtext = GetPerTupleExprContext(estate);

      /* Arrange for econtext's scan tuple to be the tuple under test */
      econtext->ecxt_scantuple = slot;

      /* And evaluate the constraints */
      for (i = 0; i < ncheck; i++)
      {
            qual = resultRelInfo->ri_ConstraintExprs[i];

            /*
             * NOTE: SQL92 specifies that a NULL result from a constraint
             * expression is not to be treated as a failure.  Therefore, tell
             * ExecQual to return TRUE for NULL.
             */
            if (!ExecQual(qual, econtext, true))
                  return check[i].ccname;
      }

      /* NULL result means no error */
      return NULL;
}

void
ExecConstraints(ResultRelInfo *resultRelInfo,
                        TupleTableSlot *slot, EState *estate)
{
      Relation    rel = resultRelInfo->ri_RelationDesc;
      TupleConstr *constr = rel->rd_att->constr;

      Assert(constr);

      if (constr->has_not_null)
      {
            int               natts = rel->rd_att->natts;
            int               attrChk;

            for (attrChk = 1; attrChk <= natts; attrChk++)
            {
                  if (rel->rd_att->attrs[attrChk - 1]->attnotnull &&
                        slot_attisnull(slot, attrChk))
                        ereport(ERROR,
                                    (errcode(ERRCODE_NOT_NULL_VIOLATION),
                                     errmsg("null value in column \"%s\" violates not-null constraint",
                                    NameStr(rel->rd_att->attrs[attrChk - 1]->attname))));
            }
      }

      if (constr->num_check > 0)
      {
            const char *failed;

            if ((failed = ExecRelCheck(resultRelInfo, slot, estate)) != NULL)
                  ereport(ERROR,
                              (errcode(ERRCODE_CHECK_VIOLATION),
                               errmsg("new row for relation \"%s\" violates check constraint \"%s\"",
                                          RelationGetRelationName(rel), failed)));
      }
}

/*
 * ExecProcessReturning --- evaluate a RETURNING list and send to dest
 *
 * projectReturning: RETURNING projection info for current result rel
 * tupleSlot: slot holding tuple actually inserted/updated/deleted
 * planSlot: slot holding tuple returned by top plan node
 * dest: where to send the output
 */
static void
ExecProcessReturning(ProjectionInfo *projectReturning,
                               TupleTableSlot *tupleSlot,
                               TupleTableSlot *planSlot,
                               DestReceiver *dest)
{
      ExprContext *econtext = projectReturning->pi_exprContext;
      TupleTableSlot *retSlot;

      /*
       * 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 */
      retSlot = ExecProject(projectReturning, NULL);

      /* Send to dest */
      (*dest->receiveSlot) (retSlot, dest);

      ExecClearTuple(retSlot);
}

/*
 * Check a modified tuple to see if we want to process its updated version
 * under READ COMMITTED rules.
 *
 * See backend/executor/README for some info about how this works.
 *
 *    estate - executor state data
 *    rti - rangetable index of table containing tuple
 *    *tid - t_ctid from the outdated tuple (ie, next updated version)
 *    priorXmax - t_xmax from the outdated tuple
 *
 * *tid is also an output parameter: it's modified to hold the TID of the
 * latest version of the tuple (note this may be changed even on failure)
 *
 * Returns a slot containing the new candidate update/delete tuple, or
 * NULL if we determine we shouldn't process the row.
 */
TupleTableSlot *
EvalPlanQual(EState *estate, Index rti,
                   ItemPointer tid, TransactionId priorXmax)
{
      evalPlanQual *epq;
      EState         *epqstate;
      Relation    relation;
      HeapTupleData tuple;
      HeapTuple   copyTuple = NULL;
      SnapshotData SnapshotDirty;
      bool        endNode;

      Assert(rti != 0);

      /*
       * find relation containing target tuple
       */
      if (estate->es_result_relation_info != NULL &&
            estate->es_result_relation_info->ri_RangeTableIndex == rti)
            relation = estate->es_result_relation_info->ri_RelationDesc;
      else
      {
            ListCell   *l;

            relation = NULL;
            foreach(l, estate->es_rowMarks)
            {
                  ExecRowMark *erm = lfirst(l);

                  if (erm->rti == rti)
                  {
                        relation = erm->relation;
                        break;
                  }
            }
            if (relation == NULL)
                  elog(ERROR, "could not find RowMark for RT index %u", rti);
      }

      /*
       * fetch tid tuple
       *
       * Loop here to deal with updated or busy tuples
       */
      InitDirtySnapshot(SnapshotDirty);
      tuple.t_self = *tid;
      for (;;)
      {
            Buffer            buffer;

            if (heap_fetch(relation, &SnapshotDirty, &tuple, &buffer, true, NULL))
            {
                  /*
                   * If xmin isn't what we're expecting, the slot must have been
                   * recycled and reused for an unrelated tuple.  This implies that
                   * the latest version of the row was deleted, so we need do
                   * nothing.  (Should be safe to examine xmin without getting
                   * buffer's content lock, since xmin never changes in an existing
                   * tuple.)
                   */
                  if (!TransactionIdEquals(HeapTupleHeaderGetXmin(tuple.t_data),
                                                       priorXmax))
                  {
                        ReleaseBuffer(buffer);
                        return NULL;
                  }

                  /* otherwise xmin should not be dirty... */
                  if (TransactionIdIsValid(SnapshotDirty.xmin))
                        elog(ERROR, "t_xmin is uncommitted in tuple to be updated");

                  /*
                   * If tuple is being updated by other transaction then we have to
                   * wait for its commit/abort.
                   */
                  if (TransactionIdIsValid(SnapshotDirty.xmax))
                  {
                        ReleaseBuffer(buffer);
                        XactLockTableWait(SnapshotDirty.xmax);
                        continue;         /* loop back to repeat heap_fetch */
                  }

                  /*
                   * If tuple was inserted by our own transaction, we have to check
                   * cmin against es_output_cid: cmin >= current CID means our
                   * command cannot see the tuple, so we should ignore it.  Without
                   * this we are open to the "Halloween problem" of indefinitely
                   * re-updating the same tuple. (We need not check cmax because
                   * HeapTupleSatisfiesDirty will consider a tuple deleted by our
                   * transaction dead, regardless of cmax.)  We just checked that
                   * priorXmax == xmin, so we can test that variable instead of
                   * doing HeapTupleHeaderGetXmin again.
                   */
                  if (TransactionIdIsCurrentTransactionId(priorXmax) &&
                        HeapTupleHeaderGetCmin(tuple.t_data) >= estate->es_output_cid)
                  {
                        ReleaseBuffer(buffer);
                        return NULL;
                  }

                  /*
                   * We got tuple - now copy it for use by recheck query.
                   */
                  copyTuple = heap_copytuple(&tuple);
                  ReleaseBuffer(buffer);
                  break;
            }

            /*
             * If the referenced slot was actually empty, the latest version of
             * the row must have been deleted, so we need do nothing.
             */
            if (tuple.t_data == NULL)
            {
                  ReleaseBuffer(buffer);
                  return NULL;
            }

            /*
             * As above, if xmin isn't what we're expecting, do nothing.
             */
            if (!TransactionIdEquals(HeapTupleHeaderGetXmin(tuple.t_data),
                                                 priorXmax))
            {
                  ReleaseBuffer(buffer);
                  return NULL;
            }

            /*
             * If we get here, the tuple was found but failed SnapshotDirty.
             * Assuming the xmin is either a committed xact or our own xact (as it
             * certainly should be if we're trying to modify the tuple), this must
             * mean that the row was updated or deleted by either a committed xact
             * or our own xact.  If it was deleted, we can ignore it; if it was
             * updated then chain up to the next version and repeat the whole
             * test.
             *
             * As above, it should be safe to examine xmax and t_ctid without the
             * buffer content lock, because they can't be changing.
             */
            if (ItemPointerEquals(&tuple.t_self, &tuple.t_data->t_ctid))
            {
                  /* deleted, so forget about it */
                  ReleaseBuffer(buffer);
                  return NULL;
            }

            /* updated, so look at the updated row */
            tuple.t_self = tuple.t_data->t_ctid;
            /* updated row should have xmin matching this xmax */
            priorXmax = HeapTupleHeaderGetXmax(tuple.t_data);
            ReleaseBuffer(buffer);
            /* loop back to fetch next in chain */
      }

      /*
       * For UPDATE/DELETE we have to return tid of actual row we're executing
       * PQ for.
       */
      *tid = tuple.t_self;

      /*
       * Need to run a recheck subquery.  Find or create a PQ stack entry.
       */
      epq = estate->es_evalPlanQual;
      endNode = true;

      if (epq != NULL && epq->rti == 0)
      {
            /* Top PQ stack entry is idle, so re-use it */
            Assert(!(estate->es_useEvalPlan) && epq->next == NULL);
            epq->rti = rti;
            endNode = false;
      }

      /*
       * If this is request for another RTE - Ra, - then we have to check wasn't
       * PlanQual requested for Ra already and if so then Ra' row was updated
       * again and we have to re-start old execution for Ra and forget all what
       * we done after Ra was suspended. Cool? -:))
       */
      if (epq != NULL && epq->rti != rti &&
            epq->estate->es_evTuple[rti - 1] != NULL)
      {
            do
            {
                  evalPlanQual *oldepq;

                  /* stop execution */
                  EvalPlanQualStop(epq);
                  /* pop previous PlanQual from the stack */
                  oldepq = epq->next;
                  Assert(oldepq && oldepq->rti != 0);
                  /* push current PQ to freePQ stack */
                  oldepq->free = epq;
                  epq = oldepq;
                  estate->es_evalPlanQual = epq;
            } while (epq->rti != rti);
      }

      /*
       * If we are requested for another RTE then we have to suspend execution
       * of current PlanQual and start execution for new one.
       */
      if (epq == NULL || epq->rti != rti)
      {
            /* try to reuse plan used previously */
            evalPlanQual *newepq = (epq != NULL) ? epq->free : NULL;

            if (newepq == NULL)           /* first call or freePQ stack is empty */
            {
                  newepq = (evalPlanQual *) palloc0(sizeof(evalPlanQual));
                  newepq->free = NULL;
                  newepq->estate = NULL;
                  newepq->planstate = NULL;
            }
            else
            {
                  /* recycle previously used PlanQual */
                  Assert(newepq->estate == NULL);
                  epq->free = NULL;
            }
            /* push current PQ to the stack */
            newepq->next = epq;
            epq = newepq;
            estate->es_evalPlanQual = epq;
            epq->rti = rti;
            endNode = false;
      }

      Assert(epq->rti == rti);

      /*
       * Ok - we're requested for the same RTE.  Unfortunately we still have to
       * end and restart execution of the plan, because ExecReScan wouldn't
       * ensure that upper plan nodes would reset themselves.  We could make
       * that work if insertion of the target tuple were integrated with the
       * Param mechanism somehow, so that the upper plan nodes know that their
       * children's outputs have changed.
       *
       * Note that the stack of free evalPlanQual nodes is quite useless at the
       * moment, since it only saves us from pallocing/releasing the
       * evalPlanQual nodes themselves.  But it will be useful once we implement
       * ReScan instead of end/restart for re-using PlanQual nodes.
       */
      if (endNode)
      {
            /* stop execution */
            EvalPlanQualStop(epq);
      }

      /*
       * Initialize new recheck query.
       *
       * Note: if we were re-using PlanQual plans via ExecReScan, we'd need to
       * instead copy down changeable state from the top plan (including
       * es_result_relation_info, es_junkFilter) and reset locally changeable
       * state in the epq (including es_param_exec_vals, es_evTupleNull).
       */
      EvalPlanQualStart(epq, estate, epq->next);

      /*
       * free old RTE' tuple, if any, and store target tuple where relation's
       * scan node will see it
       */
      epqstate = epq->estate;
      if (epqstate->es_evTuple[rti - 1] != NULL)
            heap_freetuple(epqstate->es_evTuple[rti - 1]);
      epqstate->es_evTuple[rti - 1] = copyTuple;

      return EvalPlanQualNext(estate);
}

static TupleTableSlot *
EvalPlanQualNext(EState *estate)
{
      evalPlanQual *epq = estate->es_evalPlanQual;
      MemoryContext oldcontext;
      TupleTableSlot *slot;

      Assert(epq->rti != 0);

lpqnext:;
      oldcontext = MemoryContextSwitchTo(epq->estate->es_query_cxt);
      slot = ExecProcNode(epq->planstate);
      MemoryContextSwitchTo(oldcontext);

      /*
       * No more tuples for this PQ. Continue previous one.
       */
      if (TupIsNull(slot))
      {
            evalPlanQual *oldepq;

            /* stop execution */
            EvalPlanQualStop(epq);
            /* pop old PQ from the stack */
            oldepq = epq->next;
            if (oldepq == NULL)
            {
                  /* this is the first (oldest) PQ - mark as free */
                  epq->rti = 0;
                  estate->es_useEvalPlan = false;
                  /* and continue Query execution */
                  return NULL;
            }
            Assert(oldepq->rti != 0);
            /* push current PQ to freePQ stack */
            oldepq->free = epq;
            epq = oldepq;
            estate->es_evalPlanQual = epq;
            goto lpqnext;
      }

      return slot;
}

static void
EndEvalPlanQual(EState *estate)
{
      evalPlanQual *epq = estate->es_evalPlanQual;

      if (epq->rti == 0)                  /* plans already shutdowned */
      {
            Assert(epq->next == NULL);
            return;
      }

      for (;;)
      {
            evalPlanQual *oldepq;

            /* stop execution */
            EvalPlanQualStop(epq);
            /* pop old PQ from the stack */
            oldepq = epq->next;
            if (oldepq == NULL)
            {
                  /* this is the first (oldest) PQ - mark as free */
                  epq->rti = 0;
                  estate->es_useEvalPlan = false;
                  break;
            }
            Assert(oldepq->rti != 0);
            /* push current PQ to freePQ stack */
            oldepq->free = epq;
            epq = oldepq;
            estate->es_evalPlanQual = epq;
      }
}

/*
 * Start execution of one level of PlanQual.
 *
 * This is a cut-down version of ExecutorStart(): we copy some state from
 * the top-level estate rather than initializing it fresh.
 */
static void
EvalPlanQualStart(evalPlanQual *epq, EState *estate, evalPlanQual *priorepq)
{
      EState         *epqstate;
      int               rtsize;
      MemoryContext oldcontext;
      ListCell   *l;

      rtsize = list_length(estate->es_range_table);

      epq->estate = epqstate = CreateExecutorState();

      oldcontext = MemoryContextSwitchTo(epqstate->es_query_cxt);

      /*
       * The epqstates share the top query's copy of unchanging state such as
       * the snapshot, rangetable, result-rel info, and external Param info.
       * They need their own copies of local state, including a tuple table,
       * es_param_exec_vals, etc.
       */
      epqstate->es_direction = ForwardScanDirection;
      epqstate->es_snapshot = estate->es_snapshot;
      epqstate->es_crosscheck_snapshot = estate->es_crosscheck_snapshot;
      epqstate->es_range_table = estate->es_range_table;
      epqstate->es_output_cid = estate->es_output_cid;
      epqstate->es_result_relations = estate->es_result_relations;
      epqstate->es_num_result_relations = estate->es_num_result_relations;
      epqstate->es_result_relation_info = estate->es_result_relation_info;
      epqstate->es_junkFilter = estate->es_junkFilter;
      /* es_trig_target_relations must NOT be copied */
      epqstate->es_param_list_info = estate->es_param_list_info;
      if (estate->es_plannedstmt->nParamExec > 0)
            epqstate->es_param_exec_vals = (ParamExecData *)
                  palloc0(estate->es_plannedstmt->nParamExec * sizeof(ParamExecData));
      epqstate->es_rowMarks = estate->es_rowMarks;
      epqstate->es_instrument = estate->es_instrument;
      epqstate->es_select_into = estate->es_select_into;
      epqstate->es_into_oids = estate->es_into_oids;
      epqstate->es_plannedstmt = estate->es_plannedstmt;

      /*
       * Each epqstate must have its own es_evTupleNull state, but all the stack
       * entries share es_evTuple state.  This allows sub-rechecks to inherit
       * the value being examined by an outer recheck.
       */
      epqstate->es_evTupleNull = (bool *) palloc0(rtsize * sizeof(bool));
      if (priorepq == NULL)
            /* first PQ stack entry */
            epqstate->es_evTuple = (HeapTuple *)
                  palloc0(rtsize * sizeof(HeapTuple));
      else
            /* later stack entries share the same storage */
            epqstate->es_evTuple = priorepq->estate->es_evTuple;

      /*
       * Create sub-tuple-table; we needn't redo the CountSlots work though.
       */
      epqstate->es_tupleTable =
            ExecCreateTupleTable(estate->es_tupleTable->size);

      /*
       * Initialize private state information for each SubPlan.  We must do this
       * before running ExecInitNode on the main query tree, since
       * ExecInitSubPlan expects to be able to find these entries.
       */
      Assert(epqstate->es_subplanstates == NIL);
      foreach(l, estate->es_plannedstmt->subplans)
      {
            Plan     *subplan = (Plan *) lfirst(l);
            PlanState  *subplanstate;

            subplanstate = ExecInitNode(subplan, epqstate, 0);

            epqstate->es_subplanstates = lappend(epqstate->es_subplanstates,
                                                                   subplanstate);
      }

      /*
       * Initialize the private state information for all the nodes in the query
       * tree.  This opens files, allocates storage and leaves us ready to start
       * processing tuples.
       */
      epq->planstate = ExecInitNode(estate->es_plannedstmt->planTree, epqstate, 0);

      MemoryContextSwitchTo(oldcontext);
}

/*
 * End execution of one level of PlanQual.
 *
 * This is a cut-down version of ExecutorEnd(); basically we want to do most
 * of the normal cleanup, but *not* close result relations (which we are
 * just sharing from the outer query).    We do, however, have to close any
 * trigger target relations that got opened, since those are not shared.
 */
static void
EvalPlanQualStop(evalPlanQual *epq)
{
      EState         *epqstate = epq->estate;
      MemoryContext oldcontext;
      ListCell   *l;

      oldcontext = MemoryContextSwitchTo(epqstate->es_query_cxt);

      ExecEndNode(epq->planstate);

      foreach(l, epqstate->es_subplanstates)
      {
            PlanState  *subplanstate = (PlanState *) lfirst(l);

            ExecEndNode(subplanstate);
      }

      ExecDropTupleTable(epqstate->es_tupleTable, true);
      epqstate->es_tupleTable = NULL;

      if (epqstate->es_evTuple[epq->rti - 1] != NULL)
      {
            heap_freetuple(epqstate->es_evTuple[epq->rti - 1]);
            epqstate->es_evTuple[epq->rti - 1] = NULL;
      }

      foreach(l, epqstate->es_trig_target_relations)
      {
            ResultRelInfo *resultRelInfo = (ResultRelInfo *) lfirst(l);

            /* Close indices and then the relation itself */
            ExecCloseIndices(resultRelInfo);
            heap_close(resultRelInfo->ri_RelationDesc, NoLock);
      }

      MemoryContextSwitchTo(oldcontext);

      FreeExecutorState(epqstate);

      epq->estate = NULL;
      epq->planstate = NULL;
}

/*
 * ExecGetActivePlanTree --- get the active PlanState tree from a QueryDesc
 *
 * Ordinarily this is just the one mentioned in the QueryDesc, but if we
 * are looking at a row returned by the EvalPlanQual machinery, we need
 * to look at the subsidiary state instead.
 */
PlanState *
ExecGetActivePlanTree(QueryDesc *queryDesc)
{
      EState         *estate = queryDesc->estate;

      if (estate && estate->es_useEvalPlan && estate->es_evalPlanQual != NULL)
            return estate->es_evalPlanQual->planstate;
      else
            return queryDesc->planstate;
}


/*
 * Support for SELECT INTO (a/k/a CREATE TABLE AS)
 *
 * We implement SELECT INTO by diverting SELECT's normal output with
 * a specialized DestReceiver type.
 */

typedef struct
{
      DestReceiver pub;             /* publicly-known function pointers */
      EState         *estate;             /* EState we are working with */
      Relation    rel;              /* Relation to write to */
      int               hi_options;       /* heap_insert performance options */
      BulkInsertState bistate;      /* bulk insert state */
} DR_intorel;

/*
 * OpenIntoRel --- actually create the SELECT INTO target relation
 *
 * This also replaces QueryDesc->dest with the special DestReceiver for
 * SELECT INTO.  We assume that the correct result tuple type has already
 * been placed in queryDesc->tupDesc.
 */
static void
OpenIntoRel(QueryDesc *queryDesc)
{
      IntoClause *into = queryDesc->plannedstmt->intoClause;
      EState         *estate = queryDesc->estate;
      Relation    intoRelationDesc;
      char     *intoName;
      Oid               namespaceId;
      Oid               tablespaceId;
      Datum       reloptions;
      AclResult   aclresult;
      Oid               intoRelationId;
      TupleDesc   tupdesc;
      DR_intorel *myState;
      static char *validnsps[] = HEAP_RELOPT_NAMESPACES;

      Assert(into);

      /*
       * Check consistency of arguments
       */
      if (into->onCommit != ONCOMMIT_NOOP && !into->rel->istemp)
            ereport(ERROR,
                        (errcode(ERRCODE_INVALID_TABLE_DEFINITION),
                         errmsg("ON COMMIT can only be used on temporary tables")));

      /*
       * Find namespace to create in, check its permissions
       */
      intoName = into->rel->relname;
      namespaceId = RangeVarGetCreationNamespace(into->rel);

      aclresult = pg_namespace_aclcheck(namespaceId, GetUserId(),
                                                        ACL_CREATE);
      if (aclresult != ACLCHECK_OK)
            aclcheck_error(aclresult, ACL_KIND_NAMESPACE,
                                 get_namespace_name(namespaceId));

      /*
       * Select tablespace to use.  If not specified, use default tablespace
       * (which may in turn default to database's default).
       */
      if (into->tableSpaceName)
      {
            tablespaceId = get_tablespace_oid(into->tableSpaceName);
            if (!OidIsValid(tablespaceId))
                  ereport(ERROR,
                              (errcode(ERRCODE_UNDEFINED_OBJECT),
                               errmsg("tablespace \"%s\" does not exist",
                                          into->tableSpaceName)));
      }
      else
      {
            tablespaceId = GetDefaultTablespace(into->rel->istemp);
            /* note InvalidOid is OK in this case */
      }

      /* Check permissions except when using the database's default space */
      if (OidIsValid(tablespaceId) && tablespaceId != MyDatabaseTableSpace)
      {
            AclResult   aclresult;

            aclresult = pg_tablespace_aclcheck(tablespaceId, GetUserId(),
                                                               ACL_CREATE);

            if (aclresult != ACLCHECK_OK)
                  aclcheck_error(aclresult, ACL_KIND_TABLESPACE,
                                       get_tablespace_name(tablespaceId));
      }

      /* Parse and validate any reloptions */
      reloptions = transformRelOptions((Datum) 0,
                                                       into->options,
                                                       NULL,
                                                       validnsps,
                                                       true,
                                                       false);
      (void) heap_reloptions(RELKIND_RELATION, reloptions, true);

      /* Copy the tupdesc because heap_create_with_catalog modifies it */
      tupdesc = CreateTupleDescCopy(queryDesc->tupDesc);

      /* Now we can actually create the new relation */
      intoRelationId = heap_create_with_catalog(intoName,
                                                                    namespaceId,
                                                                    tablespaceId,
                                                                    InvalidOid,
                                                                    GetUserId(),
                                                                    tupdesc,
                                                                    NIL,
                                                                    RELKIND_RELATION,
                                                                    false,
                                                                    true,
                                                                    0,
                                                                    into->onCommit,
                                                                    reloptions,
                                                                    allowSystemTableMods);

      FreeTupleDesc(tupdesc);

      /*
       * Advance command counter so that the newly-created relation's catalog
       * tuples will be visible to heap_open.
       */
      CommandCounterIncrement();

      /*
       * If necessary, create a TOAST table for the INTO relation. Note that
       * AlterTableCreateToastTable ends with CommandCounterIncrement(), so that
       * the TOAST table will be visible for insertion.
       */
      reloptions = transformRelOptions((Datum) 0,
                                                       into->options,
                                                       "toast",
                                                       validnsps,
                                                       true,
                                                       false);

      (void) heap_reloptions(RELKIND_TOASTVALUE, reloptions, true);

      AlterTableCreateToastTable(intoRelationId, InvalidOid, reloptions, false);

      /*
       * And open the constructed table for writing.
       */
      intoRelationDesc = heap_open(intoRelationId, AccessExclusiveLock);

      /*
       * Now replace the query's DestReceiver with one for SELECT INTO
       */
      queryDesc->dest = CreateDestReceiver(DestIntoRel);
      myState = (DR_intorel *) queryDesc->dest;
      Assert(myState->pub.mydest == DestIntoRel);
      myState->estate = estate;
      myState->rel = intoRelationDesc;

      /*
       * We can skip WAL-logging the insertions, unless PITR is in use.  We can
       * skip the FSM in any case.
       */
      myState->hi_options = HEAP_INSERT_SKIP_FSM |
            (XLogArchivingActive() ? 0 : HEAP_INSERT_SKIP_WAL);
      myState->bistate = GetBulkInsertState();

      /* Not using WAL requires rd_targblock be initially invalid */
      Assert(intoRelationDesc->rd_targblock == InvalidBlockNumber);
}

/*
 * CloseIntoRel --- clean up SELECT INTO at ExecutorEnd time
 */
static void
CloseIntoRel(QueryDesc *queryDesc)
{
      DR_intorel *myState = (DR_intorel *) queryDesc->dest;

      /* OpenIntoRel might never have gotten called */
      if (myState && myState->pub.mydest == DestIntoRel && myState->rel)
      {
            FreeBulkInsertState(myState->bistate);

            /* If we skipped using WAL, must heap_sync before commit */
            if (myState->hi_options & HEAP_INSERT_SKIP_WAL)
                  heap_sync(myState->rel);

            /* close rel, but keep lock until commit */
            heap_close(myState->rel, NoLock);

            myState->rel = NULL;
      }
}

/*
 * CreateIntoRelDestReceiver -- create a suitable DestReceiver object
 */
DestReceiver *
CreateIntoRelDestReceiver(void)
{
      DR_intorel *self = (DR_intorel *) palloc0(sizeof(DR_intorel));

      self->pub.receiveSlot = intorel_receive;
      self->pub.rStartup = intorel_startup;
      self->pub.rShutdown = intorel_shutdown;
      self->pub.rDestroy = intorel_destroy;
      self->pub.mydest = DestIntoRel;

      /* private fields will be set by OpenIntoRel */

      return (DestReceiver *) self;
}

/*
 * intorel_startup --- executor startup
 */
static void
intorel_startup(DestReceiver *self, int operation, TupleDesc typeinfo)
{
      /* no-op */
}

/*
 * intorel_receive --- receive one tuple
 */
static void
intorel_receive(TupleTableSlot *slot, DestReceiver *self)
{
      DR_intorel *myState = (DR_intorel *) self;
      HeapTuple   tuple;

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

      /*
       * force assignment of new OID (see comments in ExecInsert)
       */
      if (myState->rel->rd_rel->relhasoids)
            HeapTupleSetOid(tuple, InvalidOid);

      heap_insert(myState->rel,
                        tuple,
                        myState->estate->es_output_cid,
                        myState->hi_options,
                        myState->bistate);

      /* We know this is a newly created relation, so there are no indexes */

      IncrAppended();
}

/*
 * intorel_shutdown --- executor end
 */
static void
intorel_shutdown(DestReceiver *self)
{
      /* no-op */
}

/*
 * intorel_destroy --- release DestReceiver object
 */
static void
intorel_destroy(DestReceiver *self)
{
      pfree(self);
}

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