text: /*-------------------------------------------------------------------------
   *
   * execMain.c
   *	  top level executor interface routines
   *
   * INTERFACE ROUTINES
   *	ExecutorStart()
   *	ExecutorRun()
   *	ExecutorFinish()
   *	ExecutorEnd()
   *
   *	These four procedures are the external interface 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 must always be called at the end of
   *	execution of a plan (unless it is aborted due to error).
   *
   *	ExecutorRun accepts direction and count arguments that specify whether
   *	the plan is to be executed forwards, backwards, and for how many tuples.
   *	In some cases ExecutorRun may be called multiple times to process all
   *	the tuples for a plan.  It is also acceptable to stop short of executing
   *	the whole plan (but only if it is a SELECT).
   *
   *	ExecutorFinish must be called after the final ExecutorRun call and
   *	before ExecutorEnd.  This can be omitted only in case of EXPLAIN,
   *	which should also omit ExecutorRun.
   *
   * Portions Copyright (c) 1996-2018, PostgreSQL Global Development Group
   * Portions Copyright (c) 1994, Regents of the University of California
   *
   *
   * IDENTIFICATION
   *	  src/backend/executor/execMain.c
   *
   *-------------------------------------------------------------------------
   */
  #include "postgres.h"
  
  #include "access/htup_details.h"
  #include "access/sysattr.h"
  #include "access/transam.h"
  #include "access/xact.h"
  #include "catalog/namespace.h"
  #include "catalog/pg_publication.h"
  #include "commands/matview.h"
  #include "commands/trigger.h"
  #include "executor/execdebug.h"
  #include "foreign/fdwapi.h"
  #include "mb/pg_wchar.h"
  #include "miscadmin.h"
  #include "optimizer/clauses.h"
  #include "parser/parsetree.h"
  #include "rewrite/rewriteManip.h"
  #include "storage/bufmgr.h"
  #include "storage/lmgr.h"
  #include "tcop/utility.h"
  #include "utils/acl.h"
  #include "utils/lsyscache.h"
  #include "utils/memutils.h"
  #include "utils/partcache.h"
  #include "utils/rls.h"
  #include "utils/ruleutils.h"
  #include "utils/snapmgr.h"
  #include "utils/tqual.h"
  
  
  /* Hooks for plugins to get control in ExecutorStart/Run/Finish/End */
  ExecutorStart_hook_type ExecutorStart_hook = NULL;
  ExecutorRun_hook_type ExecutorRun_hook = NULL;
  ExecutorFinish_hook_type ExecutorFinish_hook = NULL;
  ExecutorEnd_hook_type ExecutorEnd_hook = NULL;
  
  /* Hook for plugin to get control in ExecCheckRTPerms() */
  ExecutorCheckPerms_hook_type ExecutorCheckPerms_hook = NULL;
  
  /* decls for local routines only used within this module */
  static void InitPlan(QueryDesc *queryDesc, int eflags);
  static void CheckValidRowMarkRel(Relation rel, RowMarkType markType);
  static void ExecPostprocessPlan(EState *estate);
  static void ExecEndPlan(PlanState *planstate, EState *estate);
  static void ExecutePlan(EState *estate, PlanState *planstate,
  			bool use_parallel_mode,
  			CmdType operation,
  			bool sendTuples,
  			uint64 numberTuples,
  			ScanDirection direction,
  			DestReceiver *dest,
  			bool execute_once);
  static bool ExecCheckRTEPerms(RangeTblEntry *rte);
  static bool ExecCheckRTEPermsModified(Oid relOid, Oid userid,
  						  Bitmapset *modifiedCols,
  						  AclMode requiredPerms);
  static void ExecCheckXactReadOnly(PlannedStmt *plannedstmt);
  static char *ExecBuildSlotValueDescription(Oid reloid,
  							  TupleTableSlot *slot,
  							  TupleDesc tupdesc,
  							  Bitmapset *modifiedCols,
  							  int maxfieldlen);
  static void EvalPlanQualStart(EPQState *epqstate, EState *parentestate,
  				  Plan *planTree);
  
  /*
   * Note that GetUpdatedColumns() also exists in commands/trigger.c.  There does
   * not appear to be any good header to put it into, given the structures that
   * it uses, so we let them be duplicated.  Be sure to update both if one needs
   * to be changed, however.
   */
  #define GetInsertedColumns(relinfo, estate) \
  	(rt_fetch((relinfo)->ri_RangeTableIndex, (estate)->es_range_table)->insertedCols)
  #define GetUpdatedColumns(relinfo, estate) \
  	(rt_fetch((relinfo)->ri_RangeTableIndex, (estate)->es_range_table)->updatedCols)
  
  /* 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 (which is separate
   * only because some places use QueryDescs for utility commands).  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.
  	 *
  	 * Don't allow writes in parallel mode.  Supporting UPDATE and DELETE
  	 * would require (a) storing the combocid hash in shared memory, rather
  	 * than synchronizing it just once at the start of parallelism, and (b) an
  	 * alternative to heap_update()'s reliance on xmax for mutual exclusion.
  	 * INSERT may have no such troubles, but we forbid it to simplify the
  	 * checks.
  	 *
  	 * We have lower-level defenses in CommandCounterIncrement and elsewhere
  	 * against performing unsafe operations in parallel mode, but this gives a
  	 * more user-friendly error message.
  	 */
  	if ((XactReadOnly || IsInParallelMode()) &&
  		!(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 external parameters, if any, from queryDesc; and allocate
  	 * workspace for internal parameters
  	 */
  	estate->es_param_list_info = queryDesc->params;
  
  	if (queryDesc->plannedstmt->paramExecTypes != NIL)
  	{
  		int			nParamExec;
  
  		nParamExec = list_length(queryDesc->plannedstmt->paramExecTypes);
  		estate->es_param_exec_vals = (ParamExecData *)
  			palloc0(nParamExec * sizeof(ParamExecData));
  	}
  
  	estate->es_sourceText = queryDesc->sourceText;
  
  	/*
  	 * Fill in the query environment, if any, from queryDesc.
  	 */
  	estate->es_queryEnv = queryDesc->queryEnv;
  
  	/*
  	 * If non-read-only query, set the command ID to mark output tuples with
  	 */
  	switch (queryDesc->operation)
  	{
  		case CMD_SELECT:
  
  			/*
  			 * SELECT FOR [KEY] UPDATE/SHARE and modifying CTEs need to mark
  			 * tuples
  			 */
  			if (queryDesc->plannedstmt->rowMarks != NIL ||
  				queryDesc->plannedstmt->hasModifyingCTE)
  				estate->es_output_cid = GetCurrentCommandId(true);
  
  			/*
  			 * A SELECT without modifying CTEs can't possibly queue triggers,
  			 * so force skip-triggers mode. This is just a marginal efficiency
  			 * hack, since AfterTriggerBeginQuery/AfterTriggerEndQuery aren't
  			 * all that expensive, but we might as well do it.
  			 */
  			if (!queryDesc->plannedstmt->hasModifyingCTE)
  				eflags |= EXEC_FLAG_SKIP_TRIGGERS;
  			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_top_eflags = eflags;
  	estate->es_instrument = queryDesc->instrument_options;
  	estate->es_jit_flags = queryDesc->plannedstmt->jitFlags;
  
  	/*
  	 * Set up an AFTER-trigger statement context, unless told not to, or
  	 * unless it's EXPLAIN-only mode (when ExecutorFinish won't be called).
  	 */
  	if (!(eflags & (EXEC_FLAG_SKIP_TRIGGERS | EXEC_FLAG_EXPLAIN_ONLY)))
  		AfterTriggerBeginQuery();
  
  	/*
  	 * 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.  Also note that the count limit is only applied to
   *		retrieved tuples, not for instance to those inserted/updated/deleted
   *		by a ModifyTable plan node.
   *
   *		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, uint64 count,
  			bool execute_once)
  {
  	if (ExecutorRun_hook)
  		(*ExecutorRun_hook) (queryDesc, direction, count, execute_once);
  	else
  		standard_ExecutorRun(queryDesc, direction, count, execute_once);
  }
  
  void
  standard_ExecutorRun(QueryDesc *queryDesc,
  					 ScanDirection direction, uint64 count, bool execute_once)
  {
  	EState	   *estate;
  	CmdType		operation;
  	DestReceiver *dest;
  	bool		sendTuples;
  	MemoryContext oldcontext;
  
  	/* sanity checks */
  	Assert(queryDesc != NULL);
  
  	estate = queryDesc->estate;
  
  	Assert(estate != NULL);
  	Assert(!(estate->es_top_eflags & EXEC_FLAG_EXPLAIN_ONLY));
  
  	/*
  	 * Switch into per-query memory context
  	 */
  	oldcontext = MemoryContextSwitchTo(estate->es_query_cxt);
  
  	/* Allow instrumentation of Executor 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->hasReturning);
  
  	if (sendTuples)
  		dest->rStartup(dest, operation, queryDesc->tupDesc);
  
  	/*
  	 * run plan
  	 */
  	if (!ScanDirectionIsNoMovement(direction))
  	{
  		if (execute_once && queryDesc->already_executed)
  			elog(ERROR, "can't re-execute query flagged for single execution");
  		queryDesc->already_executed = true;
  
  		ExecutePlan(estate,
  					queryDesc->planstate,
  					queryDesc->plannedstmt->parallelModeNeeded,
  					operation,
  					sendTuples,
  					count,
  					direction,
  					dest,
  					execute_once);
  	}
  
  	/*
  	 * shutdown tuple receiver, if we started it
  	 */
  	if (sendTuples)
  		dest->rShutdown(dest);
  
  	if (queryDesc->totaltime)
  		InstrStopNode(queryDesc->totaltime, estate->es_processed);
  
  	MemoryContextSwitchTo(oldcontext);
  }
  
  /* ----------------------------------------------------------------
   *		ExecutorFinish
   *
   *		This routine must be called after the last ExecutorRun call.
   *		It performs cleanup such as firing AFTER triggers.  It is
   *		separate from ExecutorEnd because EXPLAIN ANALYZE needs to
   *		include these actions in the total runtime.
   *
   *		We provide a function hook variable that lets loadable plugins
   *		get control when ExecutorFinish is called.  Such a plugin would
   *		normally call standard_ExecutorFinish().
   *
   * ----------------------------------------------------------------
   */
  void
  ExecutorFinish(QueryDesc *queryDesc)
  {
  	if (ExecutorFinish_hook)
  		(*ExecutorFinish_hook) (queryDesc);
  	else
  		standard_ExecutorFinish(queryDesc);
  }
  
  void
  standard_ExecutorFinish(QueryDesc *queryDesc)
  {
  	EState	   *estate;
  	MemoryContext oldcontext;
  
  	/* sanity checks */
  	Assert(queryDesc != NULL);
  
  	estate = queryDesc->estate;
  
  	Assert(estate != NULL);
  	Assert(!(estate->es_top_eflags & EXEC_FLAG_EXPLAIN_ONLY));
  
  	/* This should be run once and only once per Executor instance */
  	Assert(!estate->es_finished);
  
  	/* Switch into per-query memory context */
  	oldcontext = MemoryContextSwitchTo(estate->es_query_cxt);
  
  	/* Allow instrumentation of Executor overall runtime */
  	if (queryDesc->totaltime)
  		InstrStartNode(queryDesc->totaltime);
  
  	/* Run ModifyTable nodes to completion */
  	ExecPostprocessPlan(estate);
  
  	/* Execute queued AFTER triggers, unless told not to */
  	if (!(estate->es_top_eflags & EXEC_FLAG_SKIP_TRIGGERS))
  		AfterTriggerEndQuery(estate);
  
  	if (queryDesc->totaltime)
  		InstrStopNode(queryDesc->totaltime, 0);
  
  	MemoryContextSwitchTo(oldcontext);
  
  	estate->es_finished = true;
  }
  
  /* ----------------------------------------------------------------
   *		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);
  
  	/*
  	 * Check that ExecutorFinish was called, unless in EXPLAIN-only mode. This
  	 * Assert is needed because ExecutorFinish is new as of 9.1, and callers
  	 * might forget to call it.
  	 */
  	Assert(estate->es_finished ||
  		   (estate->es_top_eflags & EXEC_FLAG_EXPLAIN_ONLY));
  
  	/*
  	 * Switch into per-query memory context to run ExecEndPlan
  	 */
  	oldcontext = MemoryContextSwitchTo(estate->es_query_cxt);
  
  	ExecEndPlan(queryDesc->planstate, estate);
  
  	/* 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);
  
  	MemoryContextSwitchTo(oldcontext);
  }
  
  
  /*
   * ExecCheckRTPerms
   *		Check access permissions for all relations listed in a range table.
   *
   * Returns true if permissions are adequate.  Otherwise, throws an appropriate
   * error if ereport_on_violation is true, or simply returns false otherwise.
   *
   * Note that this does NOT address row level security policies (aka: RLS).  If
   * rows will be returned to the user as a result of this permission check
   * passing, then RLS also needs to be consulted (and check_enable_rls()).
   *
   * See rewrite/rowsecurity.c.
   */
  bool
  ExecCheckRTPerms(List *rangeTable, bool ereport_on_violation)
  {
  	ListCell   *l;
  	bool		result = true;
  
  	foreach(l, rangeTable)
  	{
  		RangeTblEntry *rte = (RangeTblEntry *) lfirst(l);
  
  		result = ExecCheckRTEPerms(rte);
  		if (!result)
  		{
  			Assert(rte->rtekind == RTE_RELATION);
  			if (ereport_on_violation)
  				aclcheck_error(ACLCHECK_NO_PRIV, get_relkind_objtype(get_rel_relkind(rte->relid)),
  							   get_rel_name(rte->relid));
  			return false;
  		}
  	}
  
  	if (ExecutorCheckPerms_hook)
  		result = (*ExecutorCheckPerms_hook) (rangeTable,
  											 ereport_on_violation);
  	return result;
  }
  
  /*
   * ExecCheckRTEPerms
   *		Check access permissions for a single RTE.
   */
  static bool
  ExecCheckRTEPerms(RangeTblEntry *rte)
  {
  	AclMode		requiredPerms;
  	AclMode		relPerms;
  	AclMode		remainingPerms;
  	Oid			relOid;
  	Oid			userid;
  
  	/*
  	 * Only plain-relation RTEs need to be checked here.  Function RTEs are
  	 * checked when the function is prepared for execution.  Join, subquery,
  	 * and special RTEs need no checks.
  	 */
  	if (rte->rtekind != RTE_RELATION)
  		return true;
  
  	/*
  	 * No work if requiredPerms is empty.
  	 */
  	requiredPerms = rte->requiredPerms;
  	if (requiredPerms == 0)
  		return true;
  
  	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)
  	{
  		int			col = -1;
  
  		/*
  		 * If we lack any permissions that exist only as relation permissions,
  		 * we can fail straight away.
  		 */
  		if (remainingPerms & ~(ACL_SELECT | ACL_INSERT | ACL_UPDATE))
  			return false;
  
  		/*
  		 * 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)
  					return false;
  			}
  
  			while ((col = bms_next_member(rte->selectedCols, col)) >= 0)
  			{
  				/* bit #s are offset by FirstLowInvalidHeapAttributeNumber */
  				AttrNumber	attno = col + FirstLowInvalidHeapAttributeNumber;
  
  				if (attno == InvalidAttrNumber)
  				{
  					/* Whole-row reference, must have priv on all cols */
  					if (pg_attribute_aclcheck_all(relOid, userid, ACL_SELECT,
  												  ACLMASK_ALL) != ACLCHECK_OK)
  						return false;
  				}
  				else
  				{
  					if (pg_attribute_aclcheck(relOid, attno, userid,
  											  ACL_SELECT) != ACLCHECK_OK)
  						return false;
  				}
  			}
  		}
  
  		/*
  		 * Basically the same for the mod columns, for both INSERT and UPDATE
  		 * privilege as specified by remainingPerms.
  		 */
  		if (remainingPerms & ACL_INSERT && !ExecCheckRTEPermsModified(relOid,
  																	  userid,
  																	  rte->insertedCols,
  																	  ACL_INSERT))
  			return false;
  
  		if (remainingPerms & ACL_UPDATE && !ExecCheckRTEPermsModified(relOid,
  																	  userid,
  																	  rte->updatedCols,
  																	  ACL_UPDATE))
  			return false;
  	}
  	return true;
  }
  
  /*
   * ExecCheckRTEPermsModified
   *		Check INSERT or UPDATE access permissions for a single RTE (these
   *		are processed uniformly).
   */
  static bool
  ExecCheckRTEPermsModified(Oid relOid, Oid userid, Bitmapset *modifiedCols,
  						  AclMode requiredPerms)
  {
  	int			col = -1;
  
  	/*
  	 * When the query doesn't explicitly update 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 UPDATE.
  	 */
  	if (bms_is_empty(modifiedCols))
  	{
  		if (pg_attribute_aclcheck_all(relOid, userid, requiredPerms,
  									  ACLMASK_ANY) != ACLCHECK_OK)
  			return false;
  	}
  
  	while ((col = bms_next_member(modifiedCols, col)) >= 0)
  	{
  		/* bit #s are offset by FirstLowInvalidHeapAttributeNumber */
  		AttrNumber	attno = col + FirstLowInvalidHeapAttributeNumber;
  
  		if (attno == InvalidAttrNumber)
  		{
  			/* whole-row reference can't happen here */
  			elog(ERROR, "whole-row update is not implemented");
  		}
  		else
  		{
  			if (pg_attribute_aclcheck(relOid, attno, userid,
  									  requiredPerms) != ACLCHECK_OK)
  				return false;
  		}
  	}
  	return true;
  }
  
  /*
   * Check that the query does not imply any writes to non-temp tables;
   * unless we're in parallel mode, in which case don't even allow writes
   * to temp tables.
   *
   * Note: in a Hot Standby this would need to reject writes to temp
   * tables just as we do in parallel mode; but an HS standby can't have created
   * any temp tables in the first place, so no need to check that.
   */
  static void
  ExecCheckXactReadOnly(PlannedStmt *plannedstmt)
  {
  	ListCell   *l;
  
  	/*
  	 * Fail if write permissions are requested in parallel mode for table
  	 * (temp or non-temp), otherwise fail for 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;
  
  		PreventCommandIfReadOnly(CreateCommandTag((Node *) plannedstmt));
  	}
  
  	if (plannedstmt->commandType != CMD_SELECT || plannedstmt->hasModifyingCTE)
  		PreventCommandIfParallelMode(CreateCommandTag((Node *) plannedstmt));
  }
  
  
  /* ----------------------------------------------------------------
   *		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, true);
  
  	/*
  	 * initialize the node's execution state
  	 */
  	estate->es_range_table = rangeTable;
  	estate->es_plannedstmt = plannedstmt;
  
  	/*
  	 * initialize result relation stuff, and open/lock the result rels.
  	 *
  	 * We must do this before initializing the plan tree, else we might try to
  	 * do a lock upgrade if a result rel is also a source rel.
  	 */
  	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,
  							  NULL,
  							  estate->es_instrument);
  			resultRelInfo++;
  		}
  		estate->es_result_relations = resultRelInfos;
  		estate->es_num_result_relations = numResultRelations;
  		/* es_result_relation_info is NULL except when within ModifyTable */
  		estate->es_result_relation_info = NULL;
  
  		/*
  		 * In the partitioned result relation case, lock the non-leaf result
  		 * relations too.  A subset of these are the roots of respective
  		 * partitioned tables, for which we also allocate ResultRelInfos.
  		 */
  		estate->es_root_result_relations = NULL;
  		estate->es_num_root_result_relations = 0;
  		if (plannedstmt->nonleafResultRelations)
  		{
  			int			num_roots = list_length(plannedstmt->rootResultRelations);
  
  			/*
  			 * Firstly, build ResultRelInfos for all the partitioned table
  			 * roots, because we will need them to fire the statement-level
  			 * triggers, if any.
  			 */
  			resultRelInfos = (ResultRelInfo *)
  				palloc(num_roots * sizeof(ResultRelInfo));
  			resultRelInfo = resultRelInfos;
  			foreach(l, plannedstmt->rootResultRelations)
  			{
  				Index		resultRelIndex = lfirst_int(l);
  				Oid			resultRelOid;
  				Relation	resultRelDesc;
  
  				resultRelOid = getrelid(resultRelIndex, rangeTable);
  				resultRelDesc = heap_open(resultRelOid, RowExclusiveLock);
  				InitResultRelInfo(resultRelInfo,
  								  resultRelDesc,
  								  lfirst_int(l),
  								  NULL,
  								  estate->es_instrument);
  				resultRelInfo++;
  			}
  
  			estate->es_root_result_relations = resultRelInfos;
  			estate->es_num_root_result_relations = num_roots;
  
  			/* Simply lock the rest of them. */
  			foreach(l, plannedstmt->nonleafResultRelations)
  			{
  				Index		resultRelIndex = lfirst_int(l);
  
  				/* We locked the roots above. */
  				if (!list_member_int(plannedstmt->rootResultRelations,
  									 resultRelIndex))
  					LockRelationOid(getrelid(resultRelIndex, rangeTable),
  									RowExclusiveLock);
  			}
  		}
  	}
  	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;
  		estate->es_root_result_relations = NULL;
  		estate->es_num_root_result_relations = 0;
  	}
  
  	/*
  	 * Similarly, we have to lock relations selected FOR [KEY] UPDATE/SHARE
  	 * before we initialize the plan tree, else we'd be risking lock upgrades.
  	 * While we are at it, build the ExecRowMark list.  Any partitioned child
  	 * tables are ignored here (because isParent=true) and will be locked by
  	 * the first Append or MergeAppend node that references them.  (Note that
  	 * the RowMarks corresponding to partitioned child tables are present in
  	 * the same list as the rest, i.e., plannedstmt->rowMarks.)
  	 */
  	estate->es_rowMarks = NIL;
  	foreach(l, plannedstmt->rowMarks)
  	{
  		PlanRowMark *rc = (PlanRowMark *) lfirst(l);
  		Oid			relid;
  		Relation	relation;
  		ExecRowMark *erm;
  
  		/* ignore "parent" rowmarks; they are irrelevant at runtime */
  		if (rc->isParent)
  			continue;
  
  		/* get relation's OID (will produce InvalidOid if subquery) */
  		relid = getrelid(rc->rti, rangeTable);
  
  		/*
  		 * If you change the conditions under which rel locks are acquired
  		 * here, be sure to adjust ExecOpenScanRelation to match.
  		 */
  		switch (rc->markType)
  		{
  			case ROW_MARK_EXCLUSIVE:
  			case ROW_MARK_NOKEYEXCLUSIVE:
  			case ROW_MARK_SHARE:
  			case ROW_MARK_KEYSHARE:
  				relation = heap_open(relid, RowShareLock);
  				break;
  			case ROW_MARK_REFERENCE:
  				relation = heap_open(relid, AccessShareLock);
  				break;
  			case ROW_MARK_COPY:
  				/* no physical table access is required */
  				relation = NULL;
  				break;
  			default:
  				elog(ERROR, "unrecognized markType: %d", rc->markType);
  				relation = NULL;	/* keep compiler quiet */
  				break;
  		}
  
  		/* Check that relation is a legal target for marking */
  		if (relation)
  			CheckValidRowMarkRel(relation, rc->markType);
  
  		erm = (ExecRowMark *) palloc(sizeof(ExecRowMark));
  		erm->relation = relation;
  		erm->relid = relid;
  		erm->rti = rc->rti;
  		erm->prti = rc->prti;
  		erm->rowmarkId = rc->rowmarkId;
  		erm->markType = rc->markType;
  		erm->strength = rc->strength;
  		erm->waitPolicy = rc->waitPolicy;
  		erm->ermActive = false;
  		ItemPointerSetInvalid(&(erm->curCtid));
  		erm->ermExtra = NULL;
  		estate->es_rowMarks = lappend(estate->es_rowMarks, erm);
  	}
  
  	/*
  	 * Initialize the executor's tuple table to empty.
  	 */
  	estate->es_tupleTable = NIL;
  	estate->es_trig_tuple_slot = NULL;
  	estate->es_trig_oldtup_slot = NULL;
  	estate->es_trig_newtup_slot = NULL;
  
  	/* mark EvalPlanQual not active */
  	estate->es_epqTuple = NULL;
  	estate->es_epqTupleSet = NULL;
  	estate->es_epqScanDone = NULL;
  
  	/*
  	 * 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 | EXEC_FLAG_WITH_NO_DATA);
  		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.
  	 */
  	tupType = ExecGetResultType(planstate);
  
  	/*
  	 * Initialize the junk filter if needed.  SELECT queries need a filter if
  	 * there are any junk attrs in the top-level tlist.
  	 */
  	if (operation == CMD_SELECT)
  	{
  		bool		junk_filter_needed = false;
  		ListCell   *tlist;
  
  		foreach(tlist, plan->targetlist)
  		{
  			TargetEntry *tle = (TargetEntry *) lfirst(tlist);
  
  			if (tle->resjunk)
  			{
  				junk_filter_needed = true;
  				break;
  			}
  		}
  
  		if (junk_filter_needed)
  		{
  			JunkFilter *j;
  
  			j = ExecInitJunkFilter(planstate->plan->targetlist,
  								   tupType->tdhasoid,
  								   ExecInitExtraTupleSlot(estate, NULL));
  			estate->es_junkFilter = j;
  
  			/* Want to return the cleaned tuple type */
  			tupType = j->jf_cleanTupType;
  		}
  	}
  
  	queryDesc->tupDesc = tupType;
  	queryDesc->planstate = planstate;
  }
  
  /*
   * Check that a proposed result relation is a legal target for the operation
   *
   * Generally the parser and/or planner should have noticed any such mistake
   * already, but let's make sure.
   *
   * Note: when changing this function, you probably also need to look at
   * CheckValidRowMarkRel.
   */
  void
  CheckValidResultRel(ResultRelInfo *resultRelInfo, CmdType operation)
  {
  	Relation	resultRel = resultRelInfo->ri_RelationDesc;
  	TriggerDesc *trigDesc = resultRel->trigdesc;
  	FdwRoutine *fdwroutine;
  
  	switch (resultRel->rd_rel->relkind)
  	{
  		case RELKIND_RELATION:
  		case RELKIND_PARTITIONED_TABLE:
  			CheckCmdReplicaIdentity(resultRel, operation);
  			break;
  		case RELKIND_SEQUENCE:
  			ereport(ERROR,
  					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  					 errmsg("cannot change sequence \"%s\"",
  							RelationGetRelationName(resultRel))));
  			break;
  		case RELKIND_TOASTVALUE:
  			ereport(ERROR,
  					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  					 errmsg("cannot change TOAST relation \"%s\"",
  							RelationGetRelationName(resultRel))));
  			break;
  		case RELKIND_VIEW:
  
  			/*
  			 * Okay only if there's a suitable INSTEAD OF trigger.  Messages
  			 * here should match rewriteHandler.c's rewriteTargetView, except
  			 * that we omit errdetail because we haven't got the information
  			 * handy (and given that we really shouldn't get here anyway, it's
  			 * not worth great exertion to get).
  			 */
  			switch (operation)
  			{
  				case CMD_INSERT:
  					if (!trigDesc || !trigDesc->trig_insert_instead_row)
  						ereport(ERROR,
  								(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
  								 errmsg("cannot insert into view \"%s\"",
  										RelationGetRelationName(resultRel)),
  								 errhint("To enable inserting into the view, provide an INSTEAD OF INSERT trigger or an unconditional ON INSERT DO INSTEAD rule.")));
  					break;
  				case CMD_UPDATE:
  					if (!trigDesc || !trigDesc->trig_update_instead_row)
  						ereport(ERROR,
  								(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
  								 errmsg("cannot update view \"%s\"",
  										RelationGetRelationName(resultRel)),
  								 errhint("To enable updating the view, provide an INSTEAD OF UPDATE trigger or an unconditional ON UPDATE DO INSTEAD rule.")));
  					break;
  				case CMD_DELETE:
  					if (!trigDesc || !trigDesc->trig_delete_instead_row)
  						ereport(ERROR,
  								(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
  								 errmsg("cannot delete from view \"%s\"",
  										RelationGetRelationName(resultRel)),
  								 errhint("To enable deleting from the view, provide an INSTEAD OF DELETE trigger or an unconditional ON DELETE DO INSTEAD rule.")));
  					break;
  				default:
  					elog(ERROR, "unrecognized CmdType: %d", (int) operation);
  					break;
  			}
  			break;
  		case RELKIND_MATVIEW:
  			if (!MatViewIncrementalMaintenanceIsEnabled())
  				ereport(ERROR,
  						(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  						 errmsg("cannot change materialized view \"%s\"",
  								RelationGetRelationName(resultRel))));
  			break;
  		case RELKIND_FOREIGN_TABLE:
  			/* Okay only if the FDW supports it */
  			fdwroutine = resultRelInfo->ri_FdwRoutine;
  			switch (operation)
  			{
  				case CMD_INSERT:
  					if (fdwroutine->ExecForeignInsert == NULL)
  						ereport(ERROR,
  								(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  								 errmsg("cannot insert into foreign table \"%s\"",
  										RelationGetRelationName(resultRel))));
  					if (fdwroutine->IsForeignRelUpdatable != NULL &&
  						(fdwroutine->IsForeignRelUpdatable(resultRel) & (1 << CMD_INSERT)) == 0)
  						ereport(ERROR,
  								(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
  								 errmsg("foreign table \"%s\" does not allow inserts",
  										RelationGetRelationName(resultRel))));
  					break;
  				case CMD_UPDATE:
  					if (fdwroutine->ExecForeignUpdate == NULL)
  						ereport(ERROR,
  								(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  								 errmsg("cannot update foreign table \"%s\"",
  										RelationGetRelationName(resultRel))));
  					if (fdwroutine->IsForeignRelUpdatable != NULL &&
  						(fdwroutine->IsForeignRelUpdatable(resultRel) & (1 << CMD_UPDATE)) == 0)
  						ereport(ERROR,
  								(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
  								 errmsg("foreign table \"%s\" does not allow updates",
  										RelationGetRelationName(resultRel))));
  					break;
  				case CMD_DELETE:
  					if (fdwroutine->ExecForeignDelete == NULL)
  						ereport(ERROR,
  								(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  								 errmsg("cannot delete from foreign table \"%s\"",
  										RelationGetRelationName(resultRel))));
  					if (fdwroutine->IsForeignRelUpdatable != NULL &&
  						(fdwroutine->IsForeignRelUpdatable(resultRel) & (1 << CMD_DELETE)) == 0)
  						ereport(ERROR,
  								(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
  								 errmsg("foreign table \"%s\" does not allow deletes",
  										RelationGetRelationName(resultRel))));
  					break;
  				default:
  					elog(ERROR, "unrecognized CmdType: %d", (int) operation);
  					break;
  			}
  			break;
  		default:
  			ereport(ERROR,
  					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  					 errmsg("cannot change relation \"%s\"",
  							RelationGetRelationName(resultRel))));
  			break;
  	}
  }
  
  /*
   * Check that a proposed rowmark target relation is a legal target
   *
   * In most cases parser and/or planner should have noticed this already, but
   * they don't cover all cases.
   */
  static void
  CheckValidRowMarkRel(Relation rel, RowMarkType markType)
  {
  	FdwRoutine *fdwroutine;
  
  	switch (rel->rd_rel->relkind)
  	{
  		case RELKIND_RELATION:
  		case RELKIND_PARTITIONED_TABLE:
  			/* OK */
  			break;
  		case RELKIND_SEQUENCE:
  			/* Must disallow this because we don't vacuum sequences */
  			ereport(ERROR,
  					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  					 errmsg("cannot lock rows in sequence \"%s\"",
  							RelationGetRelationName(rel))));
  			break;
  		case RELKIND_TOASTVALUE:
  			/* We could allow this, but there seems no good reason to */
  			ereport(ERROR,
  					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  					 errmsg("cannot lock rows in TOAST relation \"%s\"",
  							RelationGetRelationName(rel))));
  			break;
  		case RELKIND_VIEW:
  			/* Should not get here; planner should have expanded the view */
  			ereport(ERROR,
  					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  					 errmsg("cannot lock rows in view \"%s\"",
  							RelationGetRelationName(rel))));
  			break;
  		case RELKIND_MATVIEW:
  			/* Allow referencing a matview, but not actual locking clauses */
  			if (markType != ROW_MARK_REFERENCE)
  				ereport(ERROR,
  						(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  						 errmsg("cannot lock rows in materialized view \"%s\"",
  								RelationGetRelationName(rel))));
  			break;
  		case RELKIND_FOREIGN_TABLE:
  			/* Okay only if the FDW supports it */
  			fdwroutine = GetFdwRoutineForRelation(rel, false);
  			if (fdwroutine->RefetchForeignRow == NULL)
  				ereport(ERROR,
  						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  						 errmsg("cannot lock rows in foreign table \"%s\"",
  								RelationGetRelationName(rel))));
  			break;
  		default:
  			ereport(ERROR,
  					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  					 errmsg("cannot lock rows in relation \"%s\"",
  							RelationGetRelationName(rel))));
  			break;
  	}
  }
  
  /*
   * Initialize ResultRelInfo data for one result relation
   *
   * Caution: before Postgres 9.1, this function included the relkind checking
   * that's now in CheckValidResultRel, and it also did ExecOpenIndices if
   * appropriate.  Be sure callers cover those needs.
   */
  void
  InitResultRelInfo(ResultRelInfo *resultRelInfo,
  				  Relation resultRelationDesc,
  				  Index resultRelationIndex,
  				  Relation partition_root,
  				  int instrument_options)
  {
  	List	   *partition_check = NIL;
  
  	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));
  		resultRelInfo->ri_TrigWhenExprs = (ExprState **)
  			palloc0(n * sizeof(ExprState *));
  		if (instrument_options)
  			resultRelInfo->ri_TrigInstrument = InstrAlloc(n, instrument_options);
  	}
  	else
  	{
  		resultRelInfo->ri_TrigFunctions = NULL;
  		resultRelInfo->ri_TrigWhenExprs = NULL;
  		resultRelInfo->ri_TrigInstrument = NULL;
  	}
  	if (resultRelationDesc->rd_rel->relkind == RELKIND_FOREIGN_TABLE)
  		resultRelInfo->ri_FdwRoutine = GetFdwRoutineForRelation(resultRelationDesc, true);
  	else
  		resultRelInfo->ri_FdwRoutine = NULL;
  
  	/* The following fields are set later if needed */
  	resultRelInfo->ri_FdwState = NULL;
  	resultRelInfo->ri_usesFdwDirectModify = false;
  	resultRelInfo->ri_ConstraintExprs = NULL;
  	resultRelInfo->ri_junkFilter = NULL;
  	resultRelInfo->ri_projectReturning = NULL;
  	resultRelInfo->ri_onConflictArbiterIndexes = NIL;
  	resultRelInfo->ri_onConflict = NULL;
  
  	/*
  	 * Partition constraint, which also includes the partition constraint of
  	 * all the ancestors that are partitions.  Note that it will be checked
  	 * even in the case of tuple-routing where this table is the target leaf
  	 * partition, if there any BR triggers defined on the table.  Although
  	 * tuple-routing implicitly preserves the partition constraint of the
  	 * target partition for a given row, the BR triggers may change the row
  	 * such that the constraint is no longer satisfied, which we must fail for
  	 * by checking it explicitly.
  	 *
  	 * If this is a partitioned table, the partition constraint (if any) of a
  	 * given row will be checked just before performing tuple-routing.
  	 */
  	partition_check = RelationGetPartitionQual(resultRelationDesc);
  
  	resultRelInfo->ri_PartitionCheck = partition_check;
  	resultRelInfo->ri_PartitionRoot = partition_root;
  	resultRelInfo->ri_PartitionReadyForRouting = false;
  }
  
  /*
   *		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, the
   * es_root_result_relations array (if any), or the es_leaf_result_relations
   * list (if any).  (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--;
  	}
  	/* Second, search through the root result relations, if any */
  	rInfo = estate->es_root_result_relations;
  	nr = estate->es_num_root_result_relations;
  	while (nr > 0)
  	{
  		if (RelationGetRelid(rInfo->ri_RelationDesc) == relid)
  			return rInfo;
  		rInfo++;
  		nr--;
  	}
  
  	/*
  	 * Third, search through the result relations that were created during
  	 * tuple routing, if any.
  	 */
  	foreach(l, estate->es_tuple_routing_result_relations)
  	{
  		rInfo = (ResultRelInfo *) lfirst(l);
  		if (RelationGetRelid(rInfo->ri_RelationDesc) == relid)
  			return rInfo;
  	}
  	/* 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.  Also, we need not
  	 * recheck the relkind, so no need for CheckValidResultRel.
  	 */
  	rel = heap_open(relid, NoLock);
  
  	/*
  	 * Make the new entry in the right context.
  	 */
  	oldcontext = MemoryContextSwitchTo(estate->es_query_cxt);
  	rInfo = makeNode(ResultRelInfo);
  	InitResultRelInfo(rInfo,
  					  rel,
  					  0,		/* dummy rangetable index */
  					  NULL,
  					  estate->es_instrument);
  	estate->es_trig_target_relations =
  		lappend(estate->es_trig_target_relations, rInfo);
  	MemoryContextSwitchTo(oldcontext);
  
  	/*
  	 * Currently, we don't need any index information in ResultRelInfos used
  	 * only for triggers, so no need to call ExecOpenIndices.
  	 */
  
  	return rInfo;
  }
  
  /*
   * Close any relations that have been opened by ExecGetTriggerResultRel().
   */
  void
  ExecCleanUpTriggerState(EState *estate)
  {
  	ListCell   *l;
  
  	foreach(l, estate->es_trig_target_relations)
  	{
  		ResultRelInfo *resultRelInfo = (ResultRelInfo *) lfirst(l);
  
  		/* Close indices and then the relation itself */
  		ExecCloseIndices(resultRelInfo);
  		heap_close(resultRelInfo->ri_RelationDesc, NoLock);
  	}
  }
  
  /*
   *		ExecContextForcesOids
   *
   * This is pretty grotty: when doing INSERT, UPDATE, or CREATE TABLE AS,
   * 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 if we are generating tuples for INSERT or UPDATE,
   * 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 subplans of
   * the ModifyTable node, so ModifyTable has to set es_result_relation_info
   * while initializing each subplan.
   *
   * CREATE TABLE AS is even uglier, because we don't have the target relation's
   * descriptor available when this code runs; we have to look aside at the
   * flags passed to ExecutorStart().
   */
  bool
  ExecContextForcesOids(PlanState *planstate, bool *hasoids)
  {
  	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;
  		}
  	}
  
  	if (planstate->state->es_top_eflags & EXEC_FLAG_WITH_OIDS)
  	{
  		*hasoids = true;
  		return true;
  	}
  	if (planstate->state->es_top_eflags & EXEC_FLAG_WITHOUT_OIDS)
  	{
  		*hasoids = false;
  		return true;
  	}
  
  	return false;
  }
  
  /* ----------------------------------------------------------------
   *		ExecPostprocessPlan
   *
   *		Give plan nodes a final chance to execute before shutdown
   * ----------------------------------------------------------------
   */
  static void
  ExecPostprocessPlan(EState *estate)
  {
  	ListCell   *lc;
  
  	/*
  	 * Make sure nodes run forward.
  	 */
  	estate->es_direction = ForwardScanDirection;
  
  	/*
  	 * Run any secondary ModifyTable nodes to completion, in case the main
  	 * query did not fetch all rows from them.  (We do this to ensure that
  	 * such nodes have predictable results.)
  	 */
  	foreach(lc, estate->es_auxmodifytables)
  	{
  		PlanState  *ps = (PlanState *) lfirst(lc);
  
  		for (;;)
  		{
  			TupleTableSlot *slot;
  
  			/* Reset the per-output-tuple exprcontext each time */
  			ResetPerTupleExprContext(estate);
  
  			slot = ExecProcNode(ps);
  
  			if (TupIsNull(slot))
  				break;
  		}
  	}
  }
  
  /* ----------------------------------------------------------------
   *		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 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's tuple table.  Actually we only care about
  	 * releasing buffer pins and tupdesc refcounts; there's no need to pfree
  	 * the TupleTableSlots, since the containing memory context is about to go
  	 * away anyway.
  	 */
  	ExecResetTupleTable(estate->es_tupleTable, false);
  
  	/*
  	 * 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++;
  	}
  
  	/* Close the root target relation(s). */
  	resultRelInfo = estate->es_root_result_relations;
  	for (i = estate->es_num_root_result_relations; i > 0; i--)
  	{
  		heap_close(resultRelInfo->ri_RelationDesc, NoLock);
  		resultRelInfo++;
  	}
  
  	/* likewise close any trigger target relations */
  	ExecCleanUpTriggerState(estate);
  
  	/*
  	 * close any relations selected FOR [KEY] UPDATE/SHARE, again keeping
  	 * locks
  	 */
  	foreach(l, estate->es_rowMarks)
  	{
  		ExecRowMark *erm = (ExecRowMark *) lfirst(l);
  
  		if (erm->relation)
  			heap_close(erm->relation, NoLock);
  	}
  }
  
  /* ----------------------------------------------------------------
   *		ExecutePlan
   *
   *		Processes the query plan until we have retrieved '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,
  			bool use_parallel_mode,
  			CmdType operation,
  			bool sendTuples,
  			uint64 numberTuples,
  			ScanDirection direction,
  			DestReceiver *dest,
  			bool execute_once)
  {
  	TupleTableSlot *slot;
  	uint64		current_tuple_count;
  
  	/*
  	 * initialize local variables
  	 */
  	current_tuple_count = 0;
  
  	/*
  	 * Set the direction.
  	 */
  	estate->es_direction = direction;
  
  	/*
  	 * If the plan might potentially be executed multiple times, we must force
  	 * it to run without parallelism, because we might exit early.
  	 */
  	if (!execute_once)
  		use_parallel_mode = false;
  
  	estate->es_use_parallel_mode = use_parallel_mode;
  	if (use_parallel_mode)
  		EnterParallelMode();
  
  	/*
  	 * 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
  		 */
  		slot = ExecProcNode(planstate);
  
  		/*
  		 * if the tuple is null, then we assume there is nothing more to
  		 * process so we just end the loop...
  		 */
  		if (TupIsNull(slot))
  		{
  			/* Allow nodes to release or shut down resources. */
  			(void) ExecShutdownNode(planstate);
  			break;
  		}
  
  		/*
  		 * 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.)
  		 */
  		if (estate->es_junkFilter != NULL)
  			slot = ExecFilterJunk(estate->es_junkFilter, slot);
  
  		/*
  		 * If we are supposed to send the tuple somewhere, do so. (In
  		 * practice, this is probably always the case at this point.)
  		 */
  		if (sendTuples)
  		{
  			/*
  			 * If we are not able to send the tuple, we assume the destination
  			 * has closed and no more tuples can be sent. If that's the case,
  			 * end the loop.
  			 */
  			if (!dest->receiveSlot(slot, dest))
  				break;
  		}
  
  		/*
  		 * Count tuples processed, if this is a SELECT.  (For other operation
  		 * types, the ModifyTable plan node must count the appropriate
  		 * events.)
  		 */
  		if (operation == CMD_SELECT)
  			(estate->es_processed)++;
  
  		/*
  		 * 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)
  		{
  			/* Allow nodes to release or shut down resources. */
  			(void) ExecShutdownNode(planstate);
  			break;
  		}
  	}
  
  	if (use_parallel_mode)
  		ExitParallelMode();
  }
  
  
  /*
   * ExecRelCheck --- check that tuple meets constraints for result relation
   *
   * Returns NULL if OK, else name of failed check constraint
   */
  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;
  	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 =
  			(ExprState **) palloc(ncheck * sizeof(ExprState *));
  		for (i = 0; i < ncheck; i++)
  		{
  			Expr	   *checkconstr;
  
  			checkconstr = stringToNode(check[i].ccbin);
  			resultRelInfo->ri_ConstraintExprs[i] =
  				ExecPrepareExpr(checkconstr, 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++)
  	{
  		ExprState  *checkconstr = resultRelInfo->ri_ConstraintExprs[i];
  
  		/*
  		 * NOTE: SQL specifies that a NULL result from a constraint expression
  		 * is not to be treated as a failure.  Therefore, use ExecCheck not
  		 * ExecQual.
  		 */
  		if (!ExecCheck(checkconstr, econtext))
  			return check[i].ccname;
  	}
  
  	/* NULL result means no error */
  	return NULL;
  }
  
  /*
   * ExecPartitionCheck --- check that tuple meets the partition constraint.
   *
   * Returns true if it meets the partition constraint.  If the constraint
   * fails and we're asked to emit to error, do so and don't return; otherwise
   * return false.
   */
  bool
  ExecPartitionCheck(ResultRelInfo *resultRelInfo, TupleTableSlot *slot,
  				   EState *estate, bool emitError)
  {
  	ExprContext *econtext;
  	bool		success;
  
  	/*
  	 * If first time through, build expression state tree for the partition
  	 * check expression.  Keep it in the per-query memory context so they'll
  	 * survive throughout the query.
  	 */
  	if (resultRelInfo->ri_PartitionCheckExpr == NULL)
  	{
  		List	   *qual = resultRelInfo->ri_PartitionCheck;
  
  		resultRelInfo->ri_PartitionCheckExpr = ExecPrepareCheck(qual, estate);
  	}
  
  	/*
  	 * 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;
  
  	/*
  	 * As in case of the catalogued constraints, we treat a NULL result as
  	 * success here, not a failure.
  	 */
  	success = ExecCheck(resultRelInfo->ri_PartitionCheckExpr, econtext);
  
  	/* if asked to emit error, don't actually return on failure */
  	if (!success && emitError)
  		ExecPartitionCheckEmitError(resultRelInfo, slot, estate);
  
  	return success;
  }
  
  /*
   * ExecPartitionCheckEmitError - Form and emit an error message after a failed
   * partition constraint check.
   */
  void
  ExecPartitionCheckEmitError(ResultRelInfo *resultRelInfo,
  							TupleTableSlot *slot,
  							EState *estate)
  {
  	Relation	rel = resultRelInfo->ri_RelationDesc;
  	Relation	orig_rel = rel;
  	TupleDesc	tupdesc = RelationGetDescr(rel);
  	char	   *val_desc;
  	Bitmapset  *modifiedCols;
  	Bitmapset  *insertedCols;
  	Bitmapset  *updatedCols;
  
  	/*
  	 * Need to first convert the tuple to the root partitioned table's row
  	 * type. For details, check similar comments in ExecConstraints().
  	 */
  	if (resultRelInfo->ri_PartitionRoot)
  	{
  		HeapTuple	tuple = ExecFetchSlotTuple(slot);
  		TupleDesc	old_tupdesc = RelationGetDescr(rel);
  		TupleConversionMap *map;
  
  		rel = resultRelInfo->ri_PartitionRoot;
  		tupdesc = RelationGetDescr(rel);
  		/* a reverse map */
  		map = convert_tuples_by_name(old_tupdesc, tupdesc,
  									 gettext_noop("could not convert row type"));
  		if (map != NULL)
  		{
  			tuple = do_convert_tuple(tuple, map);
  			ExecSetSlotDescriptor(slot, tupdesc);
  			ExecStoreTuple(tuple, slot, InvalidBuffer, false);
  		}
  	}
  
  	insertedCols = GetInsertedColumns(resultRelInfo, estate);
  	updatedCols = GetUpdatedColumns(resultRelInfo, estate);
  	modifiedCols = bms_union(insertedCols, updatedCols);
  	val_desc = ExecBuildSlotValueDescription(RelationGetRelid(rel),
  											 slot,
  											 tupdesc,
  											 modifiedCols,
  											 64);
  	ereport(ERROR,
  			(errcode(ERRCODE_CHECK_VIOLATION),
  			 errmsg("new row for relation \"%s\" violates partition constraint",
  					RelationGetRelationName(orig_rel)),
  			 val_desc ? errdetail("Failing row contains %s.", val_desc) : 0));
  }
  
  /*
   * ExecConstraints - check constraints of the tuple in 'slot'
   *
   * This checks the traditional NOT NULL and check constraints.
   *
   * The partition constraint is *NOT* checked.
   *
   * Note: 'slot' contains the tuple to check the constraints of, which may
   * have been converted from the original input tuple after tuple routing.
   * 'resultRelInfo' is the final result relation, after tuple routing.
   */
  void
  ExecConstraints(ResultRelInfo *resultRelInfo,
  				TupleTableSlot *slot, EState *estate)
  {
  	Relation	rel = resultRelInfo->ri_RelationDesc;
  	TupleDesc	tupdesc = RelationGetDescr(rel);
  	TupleConstr *constr = tupdesc->constr;
  	Bitmapset  *modifiedCols;
  	Bitmapset  *insertedCols;
  	Bitmapset  *updatedCols;
  
  	Assert(constr || resultRelInfo->ri_PartitionCheck);
  
  	if (constr && constr->has_not_null)
  	{
  		int			natts = tupdesc->natts;
  		int			attrChk;
  
  		for (attrChk = 1; attrChk <= natts; attrChk++)
  		{
  			Form_pg_attribute att = TupleDescAttr(tupdesc, attrChk - 1);
  
  			if (att->attnotnull && slot_attisnull(slot, attrChk))
  			{
  				char	   *val_desc;
  				Relation	orig_rel = rel;
  				TupleDesc	orig_tupdesc = RelationGetDescr(rel);
  
  				/*
  				 * If the tuple has been routed, it's been converted to the
  				 * partition's rowtype, which might differ from the root
  				 * table's.  We must convert it back to the root table's
  				 * rowtype so that val_desc shown error message matches the
  				 * input tuple.
  				 */
  				if (resultRelInfo->ri_PartitionRoot)
  				{
  					HeapTuple	tuple = ExecFetchSlotTuple(slot);
  					TupleConversionMap *map;
  
  					rel = resultRelInfo->ri_PartitionRoot;
  					tupdesc = RelationGetDescr(rel);
  					/* a reverse map */
  					map = convert_tuples_by_name(orig_tupdesc, tupdesc,
  												 gettext_noop("could not convert row type"));
  					if (map != NULL)
  					{
  						tuple = do_convert_tuple(tuple, map);
  						ExecSetSlotDescriptor(slot, tupdesc);
  						ExecStoreTuple(tuple, slot, InvalidBuffer, false);
  					}
  				}
  
  				insertedCols = GetInsertedColumns(resultRelInfo, estate);
  				updatedCols = GetUpdatedColumns(resultRelInfo, estate);
  				modifiedCols = bms_union(insertedCols, updatedCols);
  				val_desc = ExecBuildSlotValueDescription(RelationGetRelid(rel),
  														 slot,
  														 tupdesc,
  														 modifiedCols,
  														 64);
  
  				ereport(ERROR,
  						(errcode(ERRCODE_NOT_NULL_VIOLATION),
  						 errmsg("null value in column \"%s\" violates not-null constraint",
  								NameStr(att->attname)),
  						 val_desc ? errdetail("Failing row contains %s.", val_desc) : 0,
  						 errtablecol(orig_rel, attrChk)));
  			}
  		}
  	}
  
  	if (constr && constr->num_check > 0)
  	{
  		const char *failed;
  
  		if ((failed = ExecRelCheck(resultRelInfo, slot, estate)) != NULL)
  		{
  			char	   *val_desc;
  			Relation	orig_rel = rel;
  
  			/* See the comment above. */
  			if (resultRelInfo->ri_PartitionRoot)
  			{
  				HeapTuple	tuple = ExecFetchSlotTuple(slot);
  				TupleDesc	old_tupdesc = RelationGetDescr(rel);
  				TupleConversionMap *map;
  
  				rel = resultRelInfo->ri_PartitionRoot;
  				tupdesc = RelationGetDescr(rel);
  				/* a reverse map */
  				map = convert_tuples_by_name(old_tupdesc, tupdesc,
  											 gettext_noop("could not convert row type"));
  				if (map != NULL)
  				{
  					tuple = do_convert_tuple(tuple, map);
  					ExecSetSlotDescriptor(slot, tupdesc);
  					ExecStoreTuple(tuple, slot, InvalidBuffer, false);
  				}
  			}
  
  			insertedCols = GetInsertedColumns(resultRelInfo, estate);
  			updatedCols = GetUpdatedColumns(resultRelInfo, estate);
  			modifiedCols = bms_union(insertedCols, updatedCols);
  			val_desc = ExecBuildSlotValueDescription(RelationGetRelid(rel),
  													 slot,
  													 tupdesc,
  													 modifiedCols,
  													 64);
  			ereport(ERROR,
  					(errcode(ERRCODE_CHECK_VIOLATION),
  					 errmsg("new row for relation \"%s\" violates check constraint \"%s\"",
  							RelationGetRelationName(orig_rel), failed),
  					 val_desc ? errdetail("Failing row contains %s.", val_desc) : 0,
  					 errtableconstraint(orig_rel, failed)));
  		}
  	}
  }
  
  /*
   * ExecWithCheckOptions -- check that tuple satisfies any WITH CHECK OPTIONs
   * of the specified kind.
   *
   * Note that this needs to be called multiple times to ensure that all kinds of
   * WITH CHECK OPTIONs are handled (both those from views which have the WITH
   * CHECK OPTION set and from row level security policies).  See ExecInsert()
   * and ExecUpdate().
   */
  void
  ExecWithCheckOptions(WCOKind kind, ResultRelInfo *resultRelInfo,
  					 TupleTableSlot *slot, EState *estate)
  {
  	Relation	rel = resultRelInfo->ri_RelationDesc;
  	TupleDesc	tupdesc = RelationGetDescr(rel);
  	ExprContext *econtext;
  	ListCell   *l1,
  			   *l2;
  
  	/*
  	 * 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;
  
  	/* Check each of the constraints */
  	forboth(l1, resultRelInfo->ri_WithCheckOptions,
  			l2, resultRelInfo->ri_WithCheckOptionExprs)
  	{
  		WithCheckOption *wco = (WithCheckOption *) lfirst(l1);
  		ExprState  *wcoExpr = (ExprState *) lfirst(l2);
  
  		/*
  		 * Skip any WCOs which are not the kind we are looking for at this
  		 * time.
  		 */
  		if (wco->kind != kind)
  			continue;
  
  		/*
  		 * WITH CHECK OPTION checks are intended to ensure that the new tuple
  		 * is visible (in the case of a view) or that it passes the
  		 * 'with-check' policy (in the case of row security). If the qual
  		 * evaluates to NULL or FALSE, then the new tuple won't be included in
  		 * the view or doesn't pass the 'with-check' policy for the table.
  		 */
  		if (!ExecQual(wcoExpr, econtext))
  		{
  			char	   *val_desc;
  			Bitmapset  *modifiedCols;
  			Bitmapset  *insertedCols;
  			Bitmapset  *updatedCols;
  
  			switch (wco->kind)
  			{
  					/*
  					 * For WITH CHECK OPTIONs coming from views, we might be
  					 * able to provide the details on the row, depending on
  					 * the permissions on the relation (that is, if the user
  					 * could view it directly anyway).  For RLS violations, we
  					 * don't include the data since we don't know if the user
  					 * should be able to view the tuple as that depends on the
  					 * USING policy.
  					 */
  				case WCO_VIEW_CHECK:
  					/* See the comment in ExecConstraints(). */
  					if (resultRelInfo->ri_PartitionRoot)
  					{
  						HeapTuple	tuple = ExecFetchSlotTuple(slot);
  						TupleDesc	old_tupdesc = RelationGetDescr(rel);
  						TupleConversionMap *map;
  
  						rel = resultRelInfo->ri_PartitionRoot;
  						tupdesc = RelationGetDescr(rel);
  						/* a reverse map */
  						map = convert_tuples_by_name(old_tupdesc, tupdesc,
  													 gettext_noop("could not convert row type"));
  						if (map != NULL)
  						{
  							tuple = do_convert_tuple(tuple, map);
  							ExecSetSlotDescriptor(slot, tupdesc);
  							ExecStoreTuple(tuple, slot, InvalidBuffer, false);
  						}
  					}
  
  					insertedCols = GetInsertedColumns(resultRelInfo, estate);
  					updatedCols = GetUpdatedColumns(resultRelInfo, estate);
  					modifiedCols = bms_union(insertedCols, updatedCols);
  					val_desc = ExecBuildSlotValueDescription(RelationGetRelid(rel),
  															 slot,
  															 tupdesc,
  															 modifiedCols,
  															 64);
  
  					ereport(ERROR,
  							(errcode(ERRCODE_WITH_CHECK_OPTION_VIOLATION),
  							 errmsg("new row violates check option for view \"%s\"",
  									wco->relname),
  							 val_desc ? errdetail("Failing row contains %s.",
  												  val_desc) : 0));
  					break;
  				case WCO_RLS_INSERT_CHECK:
  				case WCO_RLS_UPDATE_CHECK:
  					if (wco->polname != NULL)
  						ereport(ERROR,
  								(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
  								 errmsg("new row violates row-level security policy \"%s\" for table \"%s\"",
  										wco->polname, wco->relname)));
  					else
  						ereport(ERROR,
  								(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
  								 errmsg("new row violates row-level security policy for table \"%s\"",
  										wco->relname)));
  					break;
  				case WCO_RLS_CONFLICT_CHECK:
  					if (wco->polname != NULL)
  						ereport(ERROR,
  								(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
  								 errmsg("new row violates row-level security policy \"%s\" (USING expression) for table \"%s\"",
  										wco->polname, wco->relname)));
  					else
  						ereport(ERROR,
  								(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
  								 errmsg("new row violates row-level security policy (USING expression) for table \"%s\"",
  										wco->relname)));
  					break;
  				default:
  					elog(ERROR, "unrecognized WCO kind: %u", wco->kind);
  					break;
  			}
  		}
  	}
  }
  
  /*
   * ExecBuildSlotValueDescription -- construct a string representing a tuple
   *
   * This is intentionally very similar to BuildIndexValueDescription, but
   * unlike that function, we truncate long field values (to at most maxfieldlen
   * bytes).  That seems necessary here since heap field values could be very
   * long, whereas index entries typically aren't so wide.
   *
   * Also, unlike the case with index entries, we need to be prepared to ignore
   * dropped columns.  We used to use the slot's tuple descriptor to decode the
   * data, but the slot's descriptor doesn't identify dropped columns, so we
   * now need to be passed the relation's descriptor.
   *
   * Note that, like BuildIndexValueDescription, if the user does not have
   * permission to view any of the columns involved, a NULL is returned.  Unlike
   * BuildIndexValueDescription, if the user has access to view a subset of the
   * column involved, that subset will be returned with a key identifying which
   * columns they are.
   */
  static char *
  ExecBuildSlotValueDescription(Oid reloid,
  							  TupleTableSlot *slot,
  							  TupleDesc tupdesc,
  							  Bitmapset *modifiedCols,
  							  int maxfieldlen)
  {
  	StringInfoData buf;
  	StringInfoData collist;
  	bool		write_comma = false;
  	bool		write_comma_collist = false;
  	int			i;
  	AclResult	aclresult;
  	bool		table_perm = false;
  	bool		any_perm = false;
  
  	/*
  	 * Check if RLS is enabled and should be active for the relation; if so,
  	 * then don't return anything.  Otherwise, go through normal permission
  	 * checks.
  	 */
  	if (check_enable_rls(reloid, InvalidOid, true) == RLS_ENABLED)
  		return NULL;
  
  	initStringInfo(&buf);
  
  	appendStringInfoChar(&buf, '(');
  
  	/*
  	 * Check if the user has permissions to see the row.  Table-level SELECT
  	 * allows access to all columns.  If the user does not have table-level
  	 * SELECT then we check each column and include those the user has SELECT
  	 * rights on.  Additionally, we always include columns the user provided
  	 * data for.
  	 */
  	aclresult = pg_class_aclcheck(reloid, GetUserId(), ACL_SELECT);
  	if (aclresult != ACLCHECK_OK)
  	{
  		/* Set up the buffer for the column list */
  		initStringInfo(&collist);
  		appendStringInfoChar(&collist, '(');
  	}
  	else
  		table_perm = any_perm = true;
  
  	/* Make sure the tuple is fully deconstructed */
  	slot_getallattrs(slot);
  
  	for (i = 0; i < tupdesc->natts; i++)
  	{
  		bool		column_perm = false;
  		char	   *val;
  		int			vallen;
  		Form_pg_attribute att = TupleDescAttr(tupdesc, i);
  
  		/* ignore dropped columns */
  		if (att->attisdropped)
  			continue;
  
  		if (!table_perm)
  		{
  			/*
  			 * No table-level SELECT, so need to make sure they either have
  			 * SELECT rights on the column or that they have provided the data
  			 * for the column.  If not, omit this column from the error
  			 * message.
  			 */
  			aclresult = pg_attribute_aclcheck(reloid, att->attnum,
  											  GetUserId(), ACL_SELECT);
  			if (bms_is_member(att->attnum - FirstLowInvalidHeapAttributeNumber,
  							  modifiedCols) || aclresult == ACLCHECK_OK)
  			{
  				column_perm = any_perm = true;
  
  				if (write_comma_collist)
  					appendStringInfoString(&collist, ", ");
  				else
  					write_comma_collist = true;
  
  				appendStringInfoString(&collist, NameStr(att->attname));
  			}
  		}
  
  		if (table_perm || column_perm)
  		{
  			if (slot->tts_isnull[i])
  				val = "null";
  			else
  			{
  				Oid			foutoid;
  				bool		typisvarlena;
  
  				getTypeOutputInfo(att->atttypid,
  								  &foutoid, &typisvarlena);
  				val = OidOutputFunctionCall(foutoid, slot->tts_values[i]);
  			}
  
  			if (write_comma)
  				appendStringInfoString(&buf, ", ");
  			else
  				write_comma = true;
  
  			/* truncate if needed */
  			vallen = strlen(val);
  			if (vallen <= maxfieldlen)
  				appendStringInfoString(&buf, val);
  			else
  			{
  				vallen = pg_mbcliplen(val, vallen, maxfieldlen);
  				appendBinaryStringInfo(&buf, val, vallen);
  				appendStringInfoString(&buf, "...");
  			}
  		}
  	}
  
  	/* If we end up with zero columns being returned, then return NULL. */
  	if (!any_perm)
  		return NULL;
  
  	appendStringInfoChar(&buf, ')');
  
  	if (!table_perm)
  	{
  		appendStringInfoString(&collist, ") = ");
  		appendStringInfoString(&collist, buf.data);
  
  		return collist.data;
  	}
  
  	return buf.data;
  }
  
  
  /*
   * ExecUpdateLockMode -- find the appropriate UPDATE tuple lock mode for a
   * given ResultRelInfo
   */
  LockTupleMode
  ExecUpdateLockMode(EState *estate, ResultRelInfo *relinfo)
  {
  	Bitmapset  *keyCols;
  	Bitmapset  *updatedCols;
  
  	/*
  	 * Compute lock mode to use.  If columns that are part of the key have not
  	 * been modified, then we can use a weaker lock, allowing for better
  	 * concurrency.
  	 */
  	updatedCols = GetUpdatedColumns(relinfo, estate);
  	keyCols = RelationGetIndexAttrBitmap(relinfo->ri_RelationDesc,
  										 INDEX_ATTR_BITMAP_KEY);
  
  	if (bms_overlap(keyCols, updatedCols))
  		return LockTupleExclusive;
  
  	return LockTupleNoKeyExclusive;
  }
  
  /*
   * ExecFindRowMark -- find the ExecRowMark struct for given rangetable index
   *
   * If no such struct, either return NULL or throw error depending on missing_ok
   */
  ExecRowMark *
  ExecFindRowMark(EState *estate, Index rti, bool missing_ok)
  {
  	ListCell   *lc;
  
  	foreach(lc, estate->es_rowMarks)
  	{
  		ExecRowMark *erm = (ExecRowMark *) lfirst(lc);
  
  		if (erm->rti == rti)
  			return erm;
  	}
  	if (!missing_ok)
  		elog(ERROR, "failed to find ExecRowMark for rangetable index %u", rti);
  	return NULL;
  }
  
  /*
   * ExecBuildAuxRowMark -- create an ExecAuxRowMark struct
   *
   * Inputs are the underlying ExecRowMark struct and the targetlist of the
   * input plan node (not planstate node!).  We need the latter to find out
   * the column numbers of the resjunk columns.
   */
  ExecAuxRowMark *
  ExecBuildAuxRowMark(ExecRowMark *erm, List *targetlist)
  {
  	ExecAuxRowMark *aerm = (ExecAuxRowMark *) palloc0(sizeof(ExecAuxRowMark));
  	char		resname[32];
  
  	aerm->rowmark = erm;
  
  	/* Look up the resjunk columns associated with this rowmark */
  	if (erm->markType != ROW_MARK_COPY)
  	{
  		/* need ctid for all methods other than COPY */
  		snprintf(resname, sizeof(resname), "ctid%u", erm->rowmarkId);
  		aerm->ctidAttNo = ExecFindJunkAttributeInTlist(targetlist,
  													   resname);
  		if (!AttributeNumberIsValid(aerm->ctidAttNo))
  			elog(ERROR, "could not find junk %s column", resname);
  	}
  	else
  	{
  		/* need wholerow if COPY */
  		snprintf(resname, sizeof(resname), "wholerow%u", erm->rowmarkId);
  		aerm->wholeAttNo = ExecFindJunkAttributeInTlist(targetlist,
  														resname);
  		if (!AttributeNumberIsValid(aerm->wholeAttNo))
  			elog(ERROR, "could not find junk %s column", resname);
  	}
  
  	/* if child rel, need tableoid */
  	if (erm->rti != erm->prti)
  	{
  		snprintf(resname, sizeof(resname), "tableoid%u", erm->rowmarkId);
  		aerm->toidAttNo = ExecFindJunkAttributeInTlist(targetlist,
  													   resname);
  		if (!AttributeNumberIsValid(aerm->toidAttNo))
  			elog(ERROR, "could not find junk %s column", resname);
  	}
  
  	return aerm;
  }
  
  
  /*
   * EvalPlanQual logic --- recheck modified tuple(s) to see if we want to
   * process the updated version under READ COMMITTED rules.
   *
   * See backend/executor/README for some info about how this works.
   */
  
  
  /*
   * Check a modified tuple to see if we want to process its updated version
   * under READ COMMITTED rules.
   *
   *	estate - outer executor state data
   *	epqstate - state for EvalPlanQual rechecking
   *	relation - table containing tuple
   *	rti - rangetable index of table containing tuple
   *	lockmode - requested tuple lock mode
   *	*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.
   *
   * Note: properly, lockmode should be declared as enum LockTupleMode,
   * but we use "int" to avoid having to include heapam.h in executor.h.
   */
  TupleTableSlot *
  EvalPlanQual(EState *estate, EPQState *epqstate,
  			 Relation relation, Index rti, int lockmode,
  			 ItemPointer tid, TransactionId priorXmax)
  {
  	TupleTableSlot *slot;
  	HeapTuple	copyTuple;
  
  	Assert(rti > 0);
  
  	/*
  	 * Get and lock the updated version of the row; if fail, return NULL.
  	 */
  	copyTuple = EvalPlanQualFetch(estate, relation, lockmode, LockWaitBlock,
  								  tid, priorXmax);
  
  	if (copyTuple == NULL)
  		return NULL;
  
  	/*
  	 * For UPDATE/DELETE we have to return tid of actual row we're executing
  	 * PQ for.
  	 */
  	*tid = copyTuple->t_self;
  
  	/*
  	 * Need to run a recheck subquery.  Initialize or reinitialize EPQ state.
  	 */
  	EvalPlanQualBegin(epqstate, estate);
  
  	/*
  	 * Free old test tuple, if any, and store new tuple where relation's scan
  	 * node will see it
  	 */
  	EvalPlanQualSetTuple(epqstate, rti, copyTuple);
  
  	/*
  	 * Fetch any non-locked source rows
  	 */
  	EvalPlanQualFetchRowMarks(epqstate);
  
  	/*
  	 * Run the EPQ query.  We assume it will return at most one tuple.
  	 */
  	slot = EvalPlanQualNext(epqstate);
  
  	/*
  	 * If we got a tuple, force the slot to materialize the tuple so that it
  	 * is not dependent on any local state in the EPQ query (in particular,
  	 * it's highly likely that the slot contains references to any pass-by-ref
  	 * datums that may be present in copyTuple).  As with the next step, this
  	 * is to guard against early re-use of the EPQ query.
  	 */
  	if (!TupIsNull(slot))
  		(void) ExecMaterializeSlot(slot);
  
  	/*
  	 * Clear out the test tuple.  This is needed in case the EPQ query is
  	 * re-used to test a tuple for a different relation.  (Not clear that can
  	 * really happen, but let's be safe.)
  	 */
  	EvalPlanQualSetTuple(epqstate, rti, NULL);
  
  	return slot;
  }
  
  /*
   * Fetch a copy of the newest version of an outdated tuple
   *
   *	estate - executor state data
   *	relation - table containing tuple
   *	lockmode - requested tuple lock mode
   *	wait_policy - requested lock wait policy
   *	*tid - t_ctid from the outdated tuple (ie, next updated version)
   *	priorXmax - t_xmax from the outdated tuple
   *
   * Returns a palloc'd copy of the newest tuple version, or NULL if we find
   * that there is no newest version (ie, the row was deleted not updated).
   * We also return NULL if the tuple is locked and the wait policy is to skip
   * such tuples.
   *
   * If successful, we have locked the newest tuple version, so caller does not
   * need to worry about it changing anymore.
   *
   * Note: properly, lockmode should be declared as enum LockTupleMode,
   * but we use "int" to avoid having to include heapam.h in executor.h.
   */
  HeapTuple
  EvalPlanQualFetch(EState *estate, Relation relation, int lockmode,
  				  LockWaitPolicy wait_policy,
  				  ItemPointer tid, TransactionId priorXmax)
  {
  	HeapTuple	copyTuple = NULL;
  	HeapTupleData tuple;
  	SnapshotData SnapshotDirty;
  
  	/*
  	 * fetch target 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))
  		{
  			HTSU_Result test;
  			HeapUpdateFailureData hufd;
  
  			/*
  			 * 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.  We assume reading a TransactionId to be
  			 * atomic, and Xmin never changes in an existing tuple, except to
  			 * invalid or frozen, and neither of those can match priorXmax.)
  			 */
  			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, or die trying.
  			 */
  			if (TransactionIdIsValid(SnapshotDirty.xmax))
  			{
  				ReleaseBuffer(buffer);
  				switch (wait_policy)
  				{
  					case LockWaitBlock:
  						XactLockTableWait(SnapshotDirty.xmax,
  										  relation, &tuple.t_self,
  										  XLTW_FetchUpdated);
  						break;
  					case LockWaitSkip:
  						if (!ConditionalXactLockTableWait(SnapshotDirty.xmax))
  							return NULL;	/* skip instead of waiting */
  						break;
  					case LockWaitError:
  						if (!ConditionalXactLockTableWait(SnapshotDirty.xmax))
  							ereport(ERROR,
  									(errcode(ERRCODE_LOCK_NOT_AVAILABLE),
  									 errmsg("could not obtain lock on row in relation \"%s\"",
  											RelationGetRelationName(relation))));
  						break;
  				}
  				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. Otherwise
  			 * heap_lock_tuple() will throw an error, and so would any later
  			 * attempt to update or delete the 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;
  			}
  
  			/*
  			 * This is a live tuple, so now try to lock it.
  			 */
  			test = heap_lock_tuple(relation, &tuple,
  								   estate->es_output_cid,
  								   lockmode, wait_policy,
  								   false, &buffer, &hufd);
  			/* We now have two pins on the buffer, get rid of one */
  			ReleaseBuffer(buffer);
  
  			switch (test)
  			{
  				case HeapTupleSelfUpdated:
  
  					/*
  					 * The target tuple was already updated or deleted by the
  					 * current command, or by a later command in the current
  					 * transaction.  We *must* ignore the tuple in the former
  					 * case, so as to avoid the "Halloween problem" of
  					 * repeated update attempts.  In the latter case it might
  					 * be sensible to fetch the updated tuple instead, but
  					 * doing so would require changing heap_update and
  					 * heap_delete to not complain about updating "invisible"
  					 * tuples, which seems pretty scary (heap_lock_tuple will
  					 * not complain, but few callers expect
  					 * HeapTupleInvisible, and we're not one of them).  So for
  					 * now, treat the tuple as deleted and do not process.
  					 */
  					ReleaseBuffer(buffer);
  					return NULL;
  
  				case HeapTupleMayBeUpdated:
  					/* successfully locked */
  					break;
  
  				case HeapTupleUpdated:
  					ReleaseBuffer(buffer);
  					if (IsolationUsesXactSnapshot())
  						ereport(ERROR,
  								(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
  								 errmsg("could not serialize access due to concurrent update")));
  					if (ItemPointerIndicatesMovedPartitions(&hufd.ctid))
  						ereport(ERROR,
  								(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
  								 errmsg("tuple to be locked was already moved to another partition due to concurrent update")));
  
  					/* Should not encounter speculative tuple on recheck */
  					Assert(!HeapTupleHeaderIsSpeculative(tuple.t_data));
  					if (!ItemPointerEquals(&hufd.ctid, &tuple.t_self))
  					{
  						/* it was updated, so look at the updated version */
  						tuple.t_self = hufd.ctid;
  						/* updated row should have xmin matching this xmax */
  						priorXmax = hufd.xmax;
  						continue;
  					}
  					/* tuple was deleted, so give up */
  					return NULL;
  
  				case HeapTupleWouldBlock:
  					ReleaseBuffer(buffer);
  					return NULL;
  
  				case HeapTupleInvisible:
  					elog(ERROR, "attempted to lock invisible tuple");
  					break;
  
  				default:
  					ReleaseBuffer(buffer);
  					elog(ERROR, "unrecognized heap_lock_tuple status: %u",
  						 test);
  					return NULL;	/* keep compiler quiet */
  			}
  
  			/*
  			 * 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
  		 * process.
  		 *
  		 * As above, it should be safe to examine xmax and t_ctid without the
  		 * buffer content lock, because they can't be changing.
  		 */
  
  		/* check whether next version would be in a different partition */
  		if (HeapTupleHeaderIndicatesMovedPartitions(tuple.t_data))
  			ereport(ERROR,
  					(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
  					 errmsg("tuple to be locked was already moved to another partition due to concurrent update")));
  
  		/* check whether tuple has been deleted */
  		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 = HeapTupleHeaderGetUpdateXid(tuple.t_data);
  		ReleaseBuffer(buffer);
  		/* loop back to fetch next in chain */
  	}
  
  	/*
  	 * Return the copied tuple
  	 */
  	return copyTuple;
  }
  
  /*
   * EvalPlanQualInit -- initialize during creation of a plan state node
   * that might need to invoke EPQ processing.
   *
   * Note: subplan/auxrowmarks can be NULL/NIL if they will be set later
   * with EvalPlanQualSetPlan.
   */
  void
  EvalPlanQualInit(EPQState *epqstate, EState *estate,
  				 Plan *subplan, List *auxrowmarks, int epqParam)
  {
  	/* Mark the EPQ state inactive */
  	epqstate->estate = NULL;
  	epqstate->planstate = NULL;
  	epqstate->origslot = NULL;
  	/* ... and remember data that EvalPlanQualBegin will need */
  	epqstate->plan = subplan;
  	epqstate->arowMarks = auxrowmarks;
  	epqstate->epqParam = epqParam;
  }
  
  /*
   * EvalPlanQualSetPlan -- set or change subplan of an EPQState.
   *
   * We need this so that ModifyTable can deal with multiple subplans.
   */
  void
  EvalPlanQualSetPlan(EPQState *epqstate, Plan *subplan, List *auxrowmarks)
  {
  	/* If we have a live EPQ query, shut it down */
  	EvalPlanQualEnd(epqstate);
  	/* And set/change the plan pointer */
  	epqstate->plan = subplan;
  	/* The rowmarks depend on the plan, too */
  	epqstate->arowMarks = auxrowmarks;
  }
  
  /*
   * Install one test tuple into EPQ state, or clear test tuple if tuple == NULL
   *
   * NB: passed tuple must be palloc'd; it may get freed later
   */
  void
  EvalPlanQualSetTuple(EPQState *epqstate, Index rti, HeapTuple tuple)
  {
  	EState	   *estate = epqstate->estate;
  
  	Assert(rti > 0);
  
  	/*
  	 * free old test tuple, if any, and store new tuple where relation's scan
  	 * node will see it
  	 */
  	if (estate->es_epqTuple[rti - 1] != NULL)
  		heap_freetuple(estate->es_epqTuple[rti - 1]);
  	estate->es_epqTuple[rti - 1] = tuple;
  	estate->es_epqTupleSet[rti - 1] = true;
  }
  
  /*
   * Fetch back the current test tuple (if any) for the specified RTI
   */
  HeapTuple
  EvalPlanQualGetTuple(EPQState *epqstate, Index rti)
  {
  	EState	   *estate = epqstate->estate;
  
  	Assert(rti > 0);
  
  	return estate->es_epqTuple[rti - 1];
  }
  
  /*
   * Fetch the current row values for any non-locked relations that need
   * to be scanned by an EvalPlanQual operation.  origslot must have been set
   * to contain the current result row (top-level row) that we need to recheck.
   */
  void
  EvalPlanQualFetchRowMarks(EPQState *epqstate)
  {
  	ListCell   *l;
  
  	Assert(epqstate->origslot != NULL);
  
  	foreach(l, epqstate->arowMarks)
  	{
  		ExecAuxRowMark *aerm = (ExecAuxRowMark *) lfirst(l);
  		ExecRowMark *erm = aerm->rowmark;
  		Datum		datum;
  		bool		isNull;
  		HeapTupleData tuple;
  
  		if (RowMarkRequiresRowShareLock(erm->markType))
  			elog(ERROR, "EvalPlanQual doesn't support locking rowmarks");
  
  		/* clear any leftover test tuple for this rel */
  		EvalPlanQualSetTuple(epqstate, erm->rti, NULL);
  
  		/* if child rel, must check whether it produced this row */
  		if (erm->rti != erm->prti)
  		{
  			Oid			tableoid;
  
  			datum = ExecGetJunkAttribute(epqstate->origslot,
  										 aerm->toidAttNo,
  										 &isNull);
  			/* non-locked rels could be on the inside of outer joins */
  			if (isNull)
  				continue;
  			tableoid = DatumGetObjectId(datum);
  
  			Assert(OidIsValid(erm->relid));
  			if (tableoid != erm->relid)
  			{
  				/* this child is inactive right now */
  				continue;
  			}
  		}
  
  		if (erm->markType == ROW_MARK_REFERENCE)
  		{
  			HeapTuple	copyTuple;
  
  			Assert(erm->relation != NULL);
  
  			/* fetch the tuple's ctid */
  			datum = ExecGetJunkAttribute(epqstate->origslot,
  										 aerm->ctidAttNo,
  										 &isNull);
  			/* non-locked rels could be on the inside of outer joins */
  			if (isNull)
  				continue;
  
  			/* fetch requests on foreign tables must be passed to their FDW */
  			if (erm->relation->rd_rel->relkind == RELKIND_FOREIGN_TABLE)
  			{
  				FdwRoutine *fdwroutine;
  				bool		updated = false;
  
  				fdwroutine = GetFdwRoutineForRelation(erm->relation, false);
  				/* this should have been checked already, but let's be safe */
  				if (fdwroutine->RefetchForeignRow == NULL)
  					ereport(ERROR,
  							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  							 errmsg("cannot lock rows in foreign table \"%s\"",
  									RelationGetRelationName(erm->relation))));
  				copyTuple = fdwroutine->RefetchForeignRow(epqstate->estate,
  														  erm,
  														  datum,
  														  &updated);
  				if (copyTuple == NULL)
  					elog(ERROR, "failed to fetch tuple for EvalPlanQual recheck");
  
  				/*
  				 * Ideally we'd insist on updated == false here, but that
  				 * assumes that FDWs can track that exactly, which they might
  				 * not be able to.  So just ignore the flag.
  				 */
  			}
  			else
  			{
  				/* ordinary table, fetch the tuple */
  				Buffer		buffer;
  
  				tuple.t_self = *((ItemPointer) DatumGetPointer(datum));
  				if (!heap_fetch(erm->relation, SnapshotAny, &tuple, &buffer,
  								false, NULL))
  					elog(ERROR, "failed to fetch tuple for EvalPlanQual recheck");
  
  				/* successful, copy tuple */
  				copyTuple = heap_copytuple(&tuple);
  				ReleaseBuffer(buffer);
  			}
  
  			/* store tuple */
  			EvalPlanQualSetTuple(epqstate, erm->rti, copyTuple);
  		}
  		else
  		{
  			HeapTupleHeader td;
  
  			Assert(erm->markType == ROW_MARK_COPY);
  
  			/* fetch the whole-row Var for the relation */
  			datum = ExecGetJunkAttribute(epqstate->origslot,
  										 aerm->wholeAttNo,
  										 &isNull);
  			/* non-locked rels could be on the inside of outer joins */
  			if (isNull)
  				continue;
  			td = DatumGetHeapTupleHeader(datum);
  
  			/* build a temporary HeapTuple control structure */
  			tuple.t_len = HeapTupleHeaderGetDatumLength(td);
  			tuple.t_data = td;
  			/* relation might be a foreign table, if so provide tableoid */
  			tuple.t_tableOid = erm->relid;
  			/* also copy t_ctid in case there's valid data there */
  			tuple.t_self = td->t_ctid;
  
  			/* copy and store tuple */
  			EvalPlanQualSetTuple(epqstate, erm->rti,
  								 heap_copytuple(&tuple));
  		}
  	}
  }
  
  /*
   * Fetch the next row (if any) from EvalPlanQual testing
   *
   * (In practice, there should never be more than one row...)
   */
  TupleTableSlot *
  EvalPlanQualNext(EPQState *epqstate)
  {
  	MemoryContext oldcontext;
  	TupleTableSlot *slot;
  
  	oldcontext = MemoryContextSwitchTo(epqstate->estate->es_query_cxt);
  	slot = ExecProcNode(epqstate->planstate);
  	MemoryContextSwitchTo(oldcontext);
  
  	return slot;
  }
  
  /*
   * Initialize or reset an EvalPlanQual state tree
   */
  void
  EvalPlanQualBegin(EPQState *epqstate, EState *parentestate)
  {
  	EState	   *estate = epqstate->estate;
  
  	if (estate == NULL)
  	{
  		/* First time through, so create a child EState */
  		EvalPlanQualStart(epqstate, parentestate, epqstate->plan);
  	}
  	else
  	{
  		/*
  		 * We already have a suitable child EPQ tree, so just reset it.
  		 */
  		int			rtsize = list_length(parentestate->es_range_table);
  		PlanState  *planstate = epqstate->planstate;
  
  		MemSet(estate->es_epqScanDone, 0, rtsize * sizeof(bool));
  
  		/* Recopy current values of parent parameters */
  		if (parentestate->es_plannedstmt->paramExecTypes != NIL)
  		{
  			int			i;
  
  			i = list_length(parentestate->es_plannedstmt->paramExecTypes);
  
  			while (--i >= 0)
  			{
  				/* copy value if any, but not execPlan link */
  				estate->es_param_exec_vals[i].value =
  					parentestate->es_param_exec_vals[i].value;
  				estate->es_param_exec_vals[i].isnull =
  					parentestate->es_param_exec_vals[i].isnull;
  			}
  		}
  
  		/*
  		 * Mark child plan tree as needing rescan at all scan nodes.  The
  		 * first ExecProcNode will take care of actually doing the rescan.
  		 */
  		planstate->chgParam = bms_add_member(planstate->chgParam,
  											 epqstate->epqParam);
  	}
  }
  
  /*
   * Start execution of an EvalPlanQual plan tree.
   *
   * 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(EPQState *epqstate, EState *parentestate, Plan *planTree)
  {
  	EState	   *estate;
  	int			rtsize;
  	MemoryContext oldcontext;
  	ListCell   *l;
  
  	rtsize = list_length(parentestate->es_range_table);
  
  	epqstate->estate = estate = CreateExecutorState();
  
  	oldcontext = MemoryContextSwitchTo(estate->es_query_cxt);
  
  	/*
  	 * Child EPQ EStates share the parent'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.
  	 *
  	 * The ResultRelInfo array management is trickier than it looks.  We
  	 * create a fresh array for the child but copy all the content from the
  	 * parent.  This is because it's okay for the child to share any
  	 * per-relation state the parent has already created --- but if the child
  	 * sets up any ResultRelInfo fields, such as its own junkfilter, that
  	 * state must *not* propagate back to the parent.  (For one thing, the
  	 * pointed-to data is in a memory context that won't last long enough.)
  	 */
  	estate->es_direction = ForwardScanDirection;
  	estate->es_snapshot = parentestate->es_snapshot;
  	estate->es_crosscheck_snapshot = parentestate->es_crosscheck_snapshot;
  	estate->es_range_table = parentestate->es_range_table;
  	estate->es_plannedstmt = parentestate->es_plannedstmt;
  	estate->es_junkFilter = parentestate->es_junkFilter;
  	estate->es_output_cid = parentestate->es_output_cid;
  	if (parentestate->es_num_result_relations > 0)
  	{
  		int			numResultRelations = parentestate->es_num_result_relations;
  		ResultRelInfo *resultRelInfos;
  
  		resultRelInfos = (ResultRelInfo *)
  			palloc(numResultRelations * sizeof(ResultRelInfo));
  		memcpy(resultRelInfos, parentestate->es_result_relations,
  			   numResultRelations * sizeof(ResultRelInfo));
  		estate->es_result_relations = resultRelInfos;
  		estate->es_num_result_relations = numResultRelations;
  	}
  	/* es_result_relation_info must NOT be copied */
  	/* es_trig_target_relations must NOT be copied */
  	estate->es_rowMarks = parentestate->es_rowMarks;
  	estate->es_top_eflags = parentestate->es_top_eflags;
  	estate->es_instrument = parentestate->es_instrument;
  	/* es_auxmodifytables must NOT be copied */
  
  	/*
  	 * The external param list is simply shared from parent.  The internal
  	 * param workspace has to be local state, but we copy the initial values
  	 * from the parent, so as to have access to any param values that were
  	 * already set from other parts of the parent's plan tree.
  	 */
  	estate->es_param_list_info = parentestate->es_param_list_info;
  	if (parentestate->es_plannedstmt->paramExecTypes != NIL)
  	{
  		int			i;
  
  		i = list_length(parentestate->es_plannedstmt->paramExecTypes);
  		estate->es_param_exec_vals = (ParamExecData *)
  			palloc0(i * sizeof(ParamExecData));
  		while (--i >= 0)
  		{
  			/* copy value if any, but not execPlan link */
  			estate->es_param_exec_vals[i].value =
  				parentestate->es_param_exec_vals[i].value;
  			estate->es_param_exec_vals[i].isnull =
  				parentestate->es_param_exec_vals[i].isnull;
  		}
  	}
  
  	/*
  	 * Each EState must have its own es_epqScanDone state, but if we have
  	 * nested EPQ checks they should share es_epqTuple arrays.  This allows
  	 * sub-rechecks to inherit the values being examined by an outer recheck.
  	 */
  	estate->es_epqScanDone = (bool *) palloc0(rtsize * sizeof(bool));
  	if (parentestate->es_epqTuple != NULL)
  	{
  		estate->es_epqTuple = parentestate->es_epqTuple;
  		estate->es_epqTupleSet = parentestate->es_epqTupleSet;
  	}
  	else
  	{
  		estate->es_epqTuple = (HeapTuple *)
  			palloc0(rtsize * sizeof(HeapTuple));
  		estate->es_epqTupleSet = (bool *)
  			palloc0(rtsize * sizeof(bool));
  	}
  
  	/*
  	 * Each estate also has its own tuple table.
  	 */
  	estate->es_tupleTable = NIL;
  
  	/*
  	 * 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. Some of the
  	 * SubPlans might not be used in the part of the plan tree we intend to
  	 * run, but since it's not easy to tell which, we just initialize them
  	 * all.
  	 */
  	Assert(estate->es_subplanstates == NIL);
  	foreach(l, parentestate->es_plannedstmt->subplans)
  	{
  		Plan	   *subplan = (Plan *) lfirst(l);
  		PlanState  *subplanstate;
  
  		subplanstate = ExecInitNode(subplan, estate, 0);
  		estate->es_subplanstates = lappend(estate->es_subplanstates,
  										   subplanstate);
  	}
  
  	/*
  	 * Initialize the private state information for all the nodes in the part
  	 * of the plan tree we need to run.  This opens files, allocates storage
  	 * and leaves us ready to start processing tuples.
  	 */
  	epqstate->planstate = ExecInitNode(planTree, estate, 0);
  
  	MemoryContextSwitchTo(oldcontext);
  }
  
  /*
   * EvalPlanQualEnd -- shut down at termination of parent plan state node,
   * or if we are done with the current EPQ child.
   *
   * 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.
   * (There probably shouldn't be any of the latter, but just in case...)
   */
  void
  EvalPlanQualEnd(EPQState *epqstate)
  {
  	EState	   *estate = epqstate->estate;
  	MemoryContext oldcontext;
  	ListCell   *l;
  
  	if (estate == NULL)
  		return;					/* idle, so nothing to do */
  
  	oldcontext = MemoryContextSwitchTo(estate->es_query_cxt);
  
  	ExecEndNode(epqstate->planstate);
  
  	foreach(l, estate->es_subplanstates)
  	{
  		PlanState  *subplanstate = (PlanState *) lfirst(l);
  
  		ExecEndNode(subplanstate);
  	}
  
  	/* throw away the per-estate tuple table */
  	ExecResetTupleTable(estate->es_tupleTable, false);
  
  	/* close any trigger target relations attached to this EState */
  	ExecCleanUpTriggerState(estate);
  
  	MemoryContextSwitchTo(oldcontext);
  
  	FreeExecutorState(estate);
  
  	/* Mark EPQState idle */
  	epqstate->estate = NULL;
  	epqstate->planstate = NULL;
  	epqstate->origslot = NULL;
  }
  