text: /*-------------------------------------------------------------------------
   *
   * nodeModifyTable.c
   *	  routines to handle ModifyTable nodes.
   *
   * Portions Copyright (c) 1996-2012, PostgreSQL Global Development Group
   * Portions Copyright (c) 1994, Regents of the University of California
   *
   *
   * IDENTIFICATION
   *	  src/backend/executor/nodeModifyTable.c
   *
   *-------------------------------------------------------------------------
   */
  /* INTERFACE ROUTINES
   *		ExecInitModifyTable - initialize the ModifyTable node
   *		ExecModifyTable		- retrieve the next tuple from the node
   *		ExecEndModifyTable	- shut down the ModifyTable node
   *		ExecReScanModifyTable - rescan the ModifyTable node
   *
   *	 NOTES
   *		Each ModifyTable node contains a list of one or more subplans,
   *		much like an Append node.  There is one subplan per result relation.
   *		The key reason for this is that in an inherited UPDATE command, each
   *		result relation could have a different schema (more or different
   *		columns) requiring a different plan tree to produce it.  In an
   *		inherited DELETE, all the subplans should produce the same output
   *		rowtype, but we might still find that different plans are appropriate
   *		for different child relations.
   *
   *		If the query specifies RETURNING, then the ModifyTable returns a
   *		RETURNING tuple after completing each row insert, update, or delete.
   *		It must be called again to continue the operation.  Without RETURNING,
   *		we just loop within the node until all the work is done, then
   *		return NULL.  This avoids useless call/return overhead.
   */
  
  #include "postgres.h"
  
  #include "access/xact.h"
  #include "commands/trigger.h"
  #include "executor/executor.h"
  #include "executor/nodeModifyTable.h"
  #include "miscadmin.h"
  #include "nodes/nodeFuncs.h"
  #include "storage/bufmgr.h"
  #include "utils/builtins.h"
  #include "utils/memutils.h"
  #include "utils/rel.h"
  #include "utils/tqual.h"
  
  
  /*
   * Verify that the tuples to be produced by INSERT or UPDATE match the
   * target relation's rowtype
   *
   * We do this to guard against stale plans.  If plan invalidation is
   * functioning properly then we should never get a failure here, but better
   * safe than sorry.  Note that this is called after we have obtained lock
   * on the target rel, so the rowtype can't change underneath us.
   *
   * The plan output is represented by its targetlist, because that makes
   * handling the dropped-column case easier.
   */
  static void
  ExecCheckPlanOutput(Relation resultRel, List *targetList)
  {
  	TupleDesc	resultDesc = RelationGetDescr(resultRel);
  	int			attno = 0;
  	ListCell   *lc;
  
  	foreach(lc, targetList)
  	{
  		TargetEntry *tle = (TargetEntry *) lfirst(lc);
  		Form_pg_attribute attr;
  
  		if (tle->resjunk)
  			continue;			/* ignore junk tlist items */
  
  		if (attno >= resultDesc->natts)
  			ereport(ERROR,
  					(errcode(ERRCODE_DATATYPE_MISMATCH),
  					 errmsg("table row type and query-specified row type do not match"),
  					 errdetail("Query has too many columns.")));
  		attr = resultDesc->attrs[attno++];
  
  		if (!attr->attisdropped)
  		{
  			/* Normal case: demand type match */
  			if (exprType((Node *) tle->expr) != attr->atttypid)
  				ereport(ERROR,
  						(errcode(ERRCODE_DATATYPE_MISMATCH),
  						 errmsg("table row type and query-specified row type do not match"),
  						 errdetail("Table has type %s at ordinal position %d, but query expects %s.",
  								   format_type_be(attr->atttypid),
  								   attno,
  							 format_type_be(exprType((Node *) tle->expr)))));
  		}
  		else
  		{
  			/*
  			 * For a dropped column, we can't check atttypid (it's likely 0).
  			 * In any case the planner has most likely inserted an INT4 null.
  			 * What we insist on is just *some* NULL constant.
  			 */
  			if (!IsA(tle->expr, Const) ||
  				!((Const *) tle->expr)->constisnull)
  				ereport(ERROR,
  						(errcode(ERRCODE_DATATYPE_MISMATCH),
  						 errmsg("table row type and query-specified row type do not match"),
  						 errdetail("Query provides a value for a dropped column at ordinal position %d.",
  								   attno)));
  		}
  	}
  	if (attno != resultDesc->natts)
  		ereport(ERROR,
  				(errcode(ERRCODE_DATATYPE_MISMATCH),
  		  errmsg("table row type and query-specified row type do not match"),
  				 errdetail("Query has too few columns.")));
  }
  
  /*
   * ExecProcessReturning --- evaluate a RETURNING list
   *
   * projectReturning: RETURNING projection info for current result rel
   * tupleSlot: slot holding tuple actually inserted/updated/deleted
   * planSlot: slot holding tuple returned by top subplan node
   *
   * Returns a slot holding the result tuple
   */
  static TupleTableSlot *
  ExecProcessReturning(ProjectionInfo *projectReturning,
  					 TupleTableSlot *tupleSlot,
  					 TupleTableSlot *planSlot)
  {
  	ExprContext *econtext = projectReturning->pi_exprContext;
  
  	/*
  	 * Reset per-tuple memory context to free any expression evaluation
  	 * storage allocated in the previous cycle.
  	 */
  	ResetExprContext(econtext);
  
  	/* Make tuple and any needed join variables available to ExecProject */
  	econtext->ecxt_scantuple = tupleSlot;
  	econtext->ecxt_outertuple = planSlot;
  
  	/* Compute the RETURNING expressions */
  	return ExecProject(projectReturning, NULL);
  }
  
  /* ----------------------------------------------------------------
   *		ExecInsert
   *
   *		For INSERT, we have to insert the tuple into the target relation
   *		and insert appropriate tuples into the index relations.
   *
   *		Returns RETURNING result if any, otherwise NULL.
   * ----------------------------------------------------------------
   */
  static TupleTableSlot *
  ExecInsert(TupleTableSlot *slot,
  		   TupleTableSlot *planSlot,
  		   EState *estate,
  		   bool canSetTag)
  {
  	HeapTuple	tuple;
  	ResultRelInfo *resultRelInfo;
  	Relation	resultRelationDesc;
  	Oid			newId;
  	List	   *recheckIndexes = NIL;
  
  	/*
  	 * get the heap tuple out of the tuple table slot, making sure we have a
  	 * writable copy
  	 */
  	tuple = ExecMaterializeSlot(slot);
  
  	/*
  	 * get information on the (current) result relation
  	 */
  	resultRelInfo = estate->es_result_relation_info;
  	resultRelationDesc = resultRelInfo->ri_RelationDesc;
  
  	/*
  	 * If the result relation has OIDs, force the tuple's OID to zero so that
  	 * heap_insert will assign a fresh OID.  Usually the OID already will be
  	 * zero at this point, but there are corner cases where the plan tree can
  	 * return a tuple extracted literally from some table with the same
  	 * rowtype.
  	 *
  	 * XXX if we ever wanted to allow users to assign their own OIDs to new
  	 * rows, this'd be the place to do it.  For the moment, we make a point of
  	 * doing this before calling triggers, so that a user-supplied trigger
  	 * could hack the OID if desired.
  	 */
  	if (resultRelationDesc->rd_rel->relhasoids)
  		HeapTupleSetOid(tuple, InvalidOid);
  
  	/* BEFORE ROW INSERT Triggers */
  	if (resultRelInfo->ri_TrigDesc &&
  		resultRelInfo->ri_TrigDesc->trig_insert_before_row)
  	{
  		slot = ExecBRInsertTriggers(estate, resultRelInfo, slot);
  
  		if (slot == NULL)		/* "do nothing" */
  			return NULL;
  
  		/* trigger might have changed tuple */
  		tuple = ExecMaterializeSlot(slot);
  	}
  
  	/* INSTEAD OF ROW INSERT Triggers */
  	if (resultRelInfo->ri_TrigDesc &&
  		resultRelInfo->ri_TrigDesc->trig_insert_instead_row)
  	{
  		slot = ExecIRInsertTriggers(estate, resultRelInfo, slot);
  
  		if (slot == NULL)		/* "do nothing" */
  			return NULL;
  
  		/* trigger might have changed tuple */
  		tuple = ExecMaterializeSlot(slot);
  
  		newId = InvalidOid;
  	}
  	else
  	{
  		/*
  		 * Check the constraints of the tuple
  		 */
  		if (resultRelationDesc->rd_att->constr)
  			ExecConstraints(resultRelInfo, slot, estate);
  
  		/*
  		 * insert the tuple
  		 *
  		 * Note: heap_insert returns the tid (location) of the new tuple in
  		 * the t_self field.
  		 */
  		newId = heap_insert(resultRelationDesc, tuple,
  							estate->es_output_cid, 0, NULL);
  
  		/*
  		 * insert index entries for tuple
  		 */
  		if (resultRelInfo->ri_NumIndices > 0)
  			recheckIndexes = ExecInsertIndexTuples(slot, &(tuple->t_self),
  												   estate);
  	}
  
  	if (canSetTag)
  	{
  		(estate->es_processed)++;
  		estate->es_lastoid = newId;
  		setLastTid(&(tuple->t_self));
  	}
  
  	/* AFTER ROW INSERT Triggers */
  	ExecARInsertTriggers(estate, resultRelInfo, tuple, recheckIndexes);
  
  	list_free(recheckIndexes);
  
  	/* Process RETURNING if present */
  	if (resultRelInfo->ri_projectReturning)
  		return ExecProcessReturning(resultRelInfo->ri_projectReturning,
  									slot, planSlot);
  
  	return NULL;
  }
  
  /* ----------------------------------------------------------------
   *		ExecDelete
   *
   *		DELETE is like UPDATE, except that we delete the tuple and no
   *		index modifications are needed.
   *
   *		When deleting from a table, tupleid identifies the tuple to
   *		delete and oldtuple is NULL.  When deleting from a view,
   *		oldtuple is passed to the INSTEAD OF triggers and identifies
   *		what to delete, and tupleid is invalid.
   *
   *		Returns RETURNING result if any, otherwise NULL.
   * ----------------------------------------------------------------
   */
  static TupleTableSlot *
  ExecDelete(ItemPointer tupleid,
  		   HeapTupleHeader oldtuple,
  		   TupleTableSlot *planSlot,
  		   EPQState *epqstate,
  		   EState *estate,
  		   bool canSetTag)
  {
  	ResultRelInfo *resultRelInfo;
  	Relation	resultRelationDesc;
  	HTSU_Result result;
  	ItemPointerData update_ctid;
  	TransactionId update_xmax;
  
  	/*
  	 * get information on the (current) result relation
  	 */
  	resultRelInfo = estate->es_result_relation_info;
  	resultRelationDesc = resultRelInfo->ri_RelationDesc;
  
  	/* BEFORE ROW DELETE Triggers */
  	if (resultRelInfo->ri_TrigDesc &&
  		resultRelInfo->ri_TrigDesc->trig_delete_before_row)
  	{
  		bool		dodelete;
  
  		dodelete = ExecBRDeleteTriggers(estate, epqstate, resultRelInfo,
  										tupleid);
  
  		if (!dodelete)			/* "do nothing" */
  			return NULL;
  	}
  
  	/* INSTEAD OF ROW DELETE Triggers */
  	if (resultRelInfo->ri_TrigDesc &&
  		resultRelInfo->ri_TrigDesc->trig_delete_instead_row)
  	{
  		HeapTupleData tuple;
  		bool		dodelete;
  
  		Assert(oldtuple != NULL);
  		tuple.t_data = oldtuple;
  		tuple.t_len = HeapTupleHeaderGetDatumLength(oldtuple);
  		ItemPointerSetInvalid(&(tuple.t_self));
  		tuple.t_tableOid = InvalidOid;
  
  		dodelete = ExecIRDeleteTriggers(estate, resultRelInfo, &tuple);
  
  		if (!dodelete)			/* "do nothing" */
  			return NULL;
  	}
  	else
  	{
  		/*
  		 * delete the tuple
  		 *
  		 * Note: if es_crosscheck_snapshot isn't InvalidSnapshot, we check
  		 * that the row to be deleted is visible to that snapshot, and throw a
  		 * can't-serialize error if not. This is a special-case behavior
  		 * needed for referential integrity updates in transaction-snapshot
  		 * mode transactions.
  		 */
  ldelete:;
  		result = heap_delete(resultRelationDesc, tupleid,
  							 &update_ctid, &update_xmax,
  							 estate->es_output_cid,
  							 estate->es_crosscheck_snapshot,
  							 true /* wait for commit */ );
  		switch (result)
  		{
  			case HeapTupleSelfUpdated:
  				/* already deleted by self; nothing to do */
  				return NULL;
  
  			case HeapTupleMayBeUpdated:
  				break;
  
  			case HeapTupleUpdated:
  				if (IsolationUsesXactSnapshot())
  					ereport(ERROR,
  							(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
  							 errmsg("could not serialize access due to concurrent update")));
  				if (!ItemPointerEquals(tupleid, &update_ctid))
  				{
  					TupleTableSlot *epqslot;
  
  					epqslot = EvalPlanQual(estate,
  										   epqstate,
  										   resultRelationDesc,
  										   resultRelInfo->ri_RangeTableIndex,
  										   &update_ctid,
  										   update_xmax);
  					if (!TupIsNull(epqslot))
  					{
  						*tupleid = update_ctid;
  						goto ldelete;
  					}
  				}
  				/* tuple already deleted; nothing to do */
  				return NULL;
  
  			default:
  				elog(ERROR, "unrecognized heap_delete status: %u", result);
  				return NULL;
  		}
  
  		/*
  		 * Note: Normally one would think that we have to delete index tuples
  		 * associated with the heap tuple now...
  		 *
  		 * ... but in POSTGRES, we have no need to do this because VACUUM will
  		 * take care of it later.  We can't delete index tuples immediately
  		 * anyway, since the tuple is still visible to other transactions.
  		 */
  	}
  
  	if (canSetTag)
  		(estate->es_processed)++;
  
  	/* AFTER ROW DELETE Triggers */
  	ExecARDeleteTriggers(estate, resultRelInfo, tupleid);
  
  	/* Process RETURNING if present */
  	if (resultRelInfo->ri_projectReturning)
  	{
  		/*
  		 * We have to put the target tuple into a slot, which means first we
  		 * gotta fetch it.  We can use the trigger tuple slot.
  		 */
  		TupleTableSlot *slot = estate->es_trig_tuple_slot;
  		TupleTableSlot *rslot;
  		HeapTupleData deltuple;
  		Buffer		delbuffer;
  
  		if (oldtuple != NULL)
  		{
  			deltuple.t_data = oldtuple;
  			deltuple.t_len = HeapTupleHeaderGetDatumLength(oldtuple);
  			ItemPointerSetInvalid(&(deltuple.t_self));
  			deltuple.t_tableOid = InvalidOid;
  			delbuffer = InvalidBuffer;
  		}
  		else
  		{
  			deltuple.t_self = *tupleid;
  			if (!heap_fetch(resultRelationDesc, SnapshotAny,
  							&deltuple, &delbuffer, false, NULL))
  				elog(ERROR, "failed to fetch deleted tuple for DELETE RETURNING");
  		}
  
  		if (slot->tts_tupleDescriptor != RelationGetDescr(resultRelationDesc))
  			ExecSetSlotDescriptor(slot, RelationGetDescr(resultRelationDesc));
  		ExecStoreTuple(&deltuple, slot, InvalidBuffer, false);
  
  		rslot = ExecProcessReturning(resultRelInfo->ri_projectReturning,
  									 slot, planSlot);
  
  		/*
  		 * Before releasing the target tuple again, make sure rslot has a
  		 * local copy of any pass-by-reference values.
  		 */
  		ExecMaterializeSlot(rslot);
  
  		ExecClearTuple(slot);
  		if (BufferIsValid(delbuffer))
  			ReleaseBuffer(delbuffer);
  
  		return rslot;
  	}
  
  	return NULL;
  }
  
  /* ----------------------------------------------------------------
   *		ExecUpdate
   *
   *		note: we can't run UPDATE queries with transactions
   *		off because UPDATEs are actually INSERTs and our
   *		scan will mistakenly loop forever, updating the tuple
   *		it just inserted..  This should be fixed but until it
   *		is, we don't want to get stuck in an infinite loop
   *		which corrupts your database..
   *
   *		When updating a table, tupleid identifies the tuple to
   *		update and oldtuple is NULL.  When updating a view, oldtuple
   *		is passed to the INSTEAD OF triggers and identifies what to
   *		update, and tupleid is invalid.
   *
   *		Returns RETURNING result if any, otherwise NULL.
   * ----------------------------------------------------------------
   */
  static TupleTableSlot *
  ExecUpdate(ItemPointer tupleid,
  		   HeapTupleHeader oldtuple,
  		   TupleTableSlot *slot,
  		   TupleTableSlot *planSlot,
  		   EPQState *epqstate,
  		   EState *estate,
  		   bool canSetTag)
  {
  	HeapTuple	tuple;
  	ResultRelInfo *resultRelInfo;
  	Relation	resultRelationDesc;
  	HTSU_Result result;
  	ItemPointerData update_ctid;
  	TransactionId update_xmax;
  	List	   *recheckIndexes = NIL;
  
  	/*
  	 * abort the operation if not running transactions
  	 */
  	if (IsBootstrapProcessingMode())
  		elog(ERROR, "cannot UPDATE during bootstrap");
  
  	/*
  	 * get the heap tuple out of the tuple table slot, making sure we have a
  	 * writable copy
  	 */
  	tuple = ExecMaterializeSlot(slot);
  
  	/*
  	 * get information on the (current) result relation
  	 */
  	resultRelInfo = estate->es_result_relation_info;
  	resultRelationDesc = resultRelInfo->ri_RelationDesc;
  
  	/* BEFORE ROW UPDATE Triggers */
  	if (resultRelInfo->ri_TrigDesc &&
  		resultRelInfo->ri_TrigDesc->trig_update_before_row)
  	{
  		slot = ExecBRUpdateTriggers(estate, epqstate, resultRelInfo,
  									tupleid, slot);
  
  		if (slot == NULL)		/* "do nothing" */
  			return NULL;
  
  		/* trigger might have changed tuple */
  		tuple = ExecMaterializeSlot(slot);
  	}
  
  	/* INSTEAD OF ROW UPDATE Triggers */
  	if (resultRelInfo->ri_TrigDesc &&
  		resultRelInfo->ri_TrigDesc->trig_update_instead_row)
  	{
  		HeapTupleData oldtup;
  
  		Assert(oldtuple != NULL);
  		oldtup.t_data = oldtuple;
  		oldtup.t_len = HeapTupleHeaderGetDatumLength(oldtuple);
  		ItemPointerSetInvalid(&(oldtup.t_self));
  		oldtup.t_tableOid = InvalidOid;
  
  		slot = ExecIRUpdateTriggers(estate, resultRelInfo,
  									&oldtup, slot);
  
  		if (slot == NULL)		/* "do nothing" */
  			return NULL;
  
  		/* trigger might have changed tuple */
  		tuple = ExecMaterializeSlot(slot);
  	}
  	else
  	{
  		/*
  		 * Check the constraints of the tuple
  		 *
  		 * If we generate a new candidate tuple after EvalPlanQual testing, we
  		 * must loop back here and recheck constraints.  (We don't need to
  		 * redo triggers, however.  If there are any BEFORE triggers then
  		 * trigger.c will have done heap_lock_tuple to lock the correct tuple,
  		 * so there's no need to do them again.)
  		 */
  lreplace:;
  		if (resultRelationDesc->rd_att->constr)
  			ExecConstraints(resultRelInfo, slot, estate);
  
  		/*
  		 * replace the heap tuple
  		 *
  		 * Note: if es_crosscheck_snapshot isn't InvalidSnapshot, we check
  		 * that the row to be updated is visible to that snapshot, and throw a
  		 * can't-serialize error if not. This is a special-case behavior
  		 * needed for referential integrity updates in transaction-snapshot
  		 * mode transactions.
  		 */
  		result = heap_update(resultRelationDesc, tupleid, tuple,
  							 &update_ctid, &update_xmax,
  							 estate->es_output_cid,
  							 estate->es_crosscheck_snapshot,
  							 true /* wait for commit */ );
  		switch (result)
  		{
  			case HeapTupleSelfUpdated:
  				/* already deleted by self; nothing to do */
  				return NULL;
  
  			case HeapTupleMayBeUpdated:
  				break;
  
  			case HeapTupleUpdated:
  				if (IsolationUsesXactSnapshot())
  					ereport(ERROR,
  							(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
  							 errmsg("could not serialize access due to concurrent update")));
  				if (!ItemPointerEquals(tupleid, &update_ctid))
  				{
  					TupleTableSlot *epqslot;
  
  					epqslot = EvalPlanQual(estate,
  										   epqstate,
  										   resultRelationDesc,
  										   resultRelInfo->ri_RangeTableIndex,
  										   &update_ctid,
  										   update_xmax);
  					if (!TupIsNull(epqslot))
  					{
  						*tupleid = update_ctid;
  						slot = ExecFilterJunk(resultRelInfo->ri_junkFilter, epqslot);
  						tuple = ExecMaterializeSlot(slot);
  						goto lreplace;
  					}
  				}
  				/* tuple already deleted; nothing to do */
  				return NULL;
  
  			default:
  				elog(ERROR, "unrecognized heap_update status: %u", result);
  				return NULL;
  		}
  
  		/*
  		 * Note: instead of having to update the old index tuples associated
  		 * with the heap tuple, all we do is form and insert new index tuples.
  		 * This is because UPDATEs are actually DELETEs and INSERTs, and index
  		 * tuple deletion is done later by VACUUM (see notes in ExecDelete).
  		 * All we do here is insert new index tuples.  -cim 9/27/89
  		 */
  
  		/*
  		 * insert index entries for tuple
  		 *
  		 * Note: heap_update returns the tid (location) of the new tuple in
  		 * the t_self field.
  		 *
  		 * If it's a HOT update, we mustn't insert new index entries.
  		 */
  		if (resultRelInfo->ri_NumIndices > 0 && !HeapTupleIsHeapOnly(tuple))
  			recheckIndexes = ExecInsertIndexTuples(slot, &(tuple->t_self),
  												   estate);
  	}
  
  	if (canSetTag)
  		(estate->es_processed)++;
  
  	/* AFTER ROW UPDATE Triggers */
  	ExecARUpdateTriggers(estate, resultRelInfo, tupleid, tuple,
  						 recheckIndexes);
  
  	list_free(recheckIndexes);
  
  	/* Process RETURNING if present */
  	if (resultRelInfo->ri_projectReturning)
  		return ExecProcessReturning(resultRelInfo->ri_projectReturning,
  									slot, planSlot);
  
  	return NULL;
  }
  
  
  /*
   * Process BEFORE EACH STATEMENT triggers
   */
  static void
  fireBSTriggers(ModifyTableState *node)
  {
  	switch (node->operation)
  	{
  		case CMD_INSERT:
  			ExecBSInsertTriggers(node->ps.state, node->resultRelInfo);
  			break;
  		case CMD_UPDATE:
  			ExecBSUpdateTriggers(node->ps.state, node->resultRelInfo);
  			break;
  		case CMD_DELETE:
  			ExecBSDeleteTriggers(node->ps.state, node->resultRelInfo);
  			break;
  		default:
  			elog(ERROR, "unknown operation");
  			break;
  	}
  }
  
  /*
   * Process AFTER EACH STATEMENT triggers
   */
  static void
  fireASTriggers(ModifyTableState *node)
  {
  	switch (node->operation)
  	{
  		case CMD_INSERT:
  			ExecASInsertTriggers(node->ps.state, node->resultRelInfo);
  			break;
  		case CMD_UPDATE:
  			ExecASUpdateTriggers(node->ps.state, node->resultRelInfo);
  			break;
  		case CMD_DELETE:
  			ExecASDeleteTriggers(node->ps.state, node->resultRelInfo);
  			break;
  		default:
  			elog(ERROR, "unknown operation");
  			break;
  	}
  }
  
  
  /* ----------------------------------------------------------------
   *	   ExecModifyTable
   *
   *		Perform table modifications as required, and return RETURNING results
   *		if needed.
   * ----------------------------------------------------------------
   */
  TupleTableSlot *
  ExecModifyTable(ModifyTableState *node)
  {
  	EState	   *estate = node->ps.state;
  	CmdType		operation = node->operation;
  	ResultRelInfo *saved_resultRelInfo;
  	ResultRelInfo *resultRelInfo;
  	PlanState  *subplanstate;
  	JunkFilter *junkfilter;
  	TupleTableSlot *slot;
  	TupleTableSlot *planSlot;
  	ItemPointer tupleid = NULL;
  	ItemPointerData tuple_ctid;
  	HeapTupleHeader oldtuple = NULL;
  
  	/*
  	 * This should NOT get called during EvalPlanQual; we should have passed a
  	 * subplan tree to EvalPlanQual, instead.  Use a runtime test not just
  	 * Assert because this condition is easy to miss in testing.  (Note:
  	 * although ModifyTable should not get executed within an EvalPlanQual
  	 * operation, we do have to allow it to be initialized and shut down in
  	 * case it is within a CTE subplan.  Hence this test must be here, not in
  	 * ExecInitModifyTable.)
  	 */
  	if (estate->es_epqTuple != NULL)
  		elog(ERROR, "ModifyTable should not be called during EvalPlanQual");
  
  	/*
  	 * If we've already completed processing, don't try to do more.  We need
  	 * this test because ExecPostprocessPlan might call us an extra time, and
  	 * our subplan's nodes aren't necessarily robust against being called
  	 * extra times.
  	 */
  	if (node->mt_done)
  		return NULL;
  
  	/*
  	 * On first call, fire BEFORE STATEMENT triggers before proceeding.
  	 */
  	if (node->fireBSTriggers)
  	{
  		fireBSTriggers(node);
  		node->fireBSTriggers = false;
  	}
  
  	/* Preload local variables */
  	resultRelInfo = node->resultRelInfo + node->mt_whichplan;
  	subplanstate = node->mt_plans[node->mt_whichplan];
  	junkfilter = resultRelInfo->ri_junkFilter;
  
  	/*
  	 * es_result_relation_info must point to the currently active result
  	 * relation while we are within this ModifyTable node.  Even though
  	 * ModifyTable nodes can't be nested statically, they can be nested
  	 * dynamically (since our subplan could include a reference to a modifying
  	 * CTE).  So we have to save and restore the caller's value.
  	 */
  	saved_resultRelInfo = estate->es_result_relation_info;
  
  	estate->es_result_relation_info = resultRelInfo;
  
  	/*
  	 * Fetch rows from subplan(s), and execute the required table modification
  	 * for each row.
  	 */
  	for (;;)
  	{
  		/*
  		 * Reset the per-output-tuple exprcontext.  This is needed because
  		 * triggers expect to use that context as workspace.  It's a bit ugly
  		 * to do this below the top level of the plan, however.  We might need
  		 * to rethink this later.
  		 */
  		ResetPerTupleExprContext(estate);
  
  		planSlot = ExecProcNode(subplanstate);
  
  		if (TupIsNull(planSlot))
  		{
  			/* advance to next subplan if any */
  			node->mt_whichplan++;
  			if (node->mt_whichplan < node->mt_nplans)
  			{
  				resultRelInfo++;
  				subplanstate = node->mt_plans[node->mt_whichplan];
  				junkfilter = resultRelInfo->ri_junkFilter;
  				estate->es_result_relation_info = resultRelInfo;
  				EvalPlanQualSetPlan(&node->mt_epqstate, subplanstate->plan,
  									node->mt_arowmarks[node->mt_whichplan]);
  				continue;
  			}
  			else
  				break;
  		}
  
  		EvalPlanQualSetSlot(&node->mt_epqstate, planSlot);
  		slot = planSlot;
  
  		if (junkfilter != NULL)
  		{
  			/*
  			 * extract the 'ctid' or 'wholerow' junk attribute.
  			 */
  			if (operation == CMD_UPDATE || operation == CMD_DELETE)
  			{
  				Datum		datum;
  				bool		isNull;
  
  				if (resultRelInfo->ri_RelationDesc->rd_rel->relkind == RELKIND_RELATION)
  				{
  					datum = ExecGetJunkAttribute(slot,
  												 junkfilter->jf_junkAttNo,
  												 &isNull);
  					/* shouldn't ever get a null result... */
  					if (isNull)
  						elog(ERROR, "ctid is NULL");
  
  					tupleid = (ItemPointer) DatumGetPointer(datum);
  					tuple_ctid = *tupleid;		/* be sure we don't free
  												 * ctid!! */
  					tupleid = &tuple_ctid;
  				}
  				else
  				{
  					datum = ExecGetJunkAttribute(slot,
  												 junkfilter->jf_junkAttNo,
  												 &isNull);
  					/* shouldn't ever get a null result... */
  					if (isNull)
  						elog(ERROR, "wholerow is NULL");
  
  					oldtuple = DatumGetHeapTupleHeader(datum);
  				}
  			}
  
  			/*
  			 * apply the junkfilter if needed.
  			 */
  			if (operation != CMD_DELETE)
  				slot = ExecFilterJunk(junkfilter, slot);
  		}
  
  		switch (operation)
  		{
  			case CMD_INSERT:
  				slot = ExecInsert(slot, planSlot, estate, node->canSetTag);
  				break;
  			case CMD_UPDATE:
  				slot = ExecUpdate(tupleid, oldtuple, slot, planSlot,
  								&node->mt_epqstate, estate, node->canSetTag);
  				break;
  			case CMD_DELETE:
  				slot = ExecDelete(tupleid, oldtuple, planSlot,
  								&node->mt_epqstate, estate, node->canSetTag);
  				break;
  			default:
  				elog(ERROR, "unknown operation");
  				break;
  		}
  
  		/*
  		 * If we got a RETURNING result, return it to caller.  We'll continue
  		 * the work on next call.
  		 */
  		if (slot)
  		{
  			estate->es_result_relation_info = saved_resultRelInfo;
  			return slot;
  		}
  	}
  
  	/* Restore es_result_relation_info before exiting */
  	estate->es_result_relation_info = saved_resultRelInfo;
  
  	/*
  	 * We're done, but fire AFTER STATEMENT triggers before exiting.
  	 */
  	fireASTriggers(node);
  
  	node->mt_done = true;
  
  	return NULL;
  }
  
  /* ----------------------------------------------------------------
   *		ExecInitModifyTable
   * ----------------------------------------------------------------
   */
  ModifyTableState *
  ExecInitModifyTable(ModifyTable *node, EState *estate, int eflags)
  {
  	ModifyTableState *mtstate;
  	CmdType		operation = node->operation;
  	int			nplans = list_length(node->plans);
  	ResultRelInfo *saved_resultRelInfo;
  	ResultRelInfo *resultRelInfo;
  	TupleDesc	tupDesc;
  	Plan	   *subplan;
  	ListCell   *l;
  	int			i;
  
  	/* check for unsupported flags */
  	Assert(!(eflags & (EXEC_FLAG_BACKWARD | EXEC_FLAG_MARK)));
  
  	/*
  	 * create state structure
  	 */
  	mtstate = makeNode(ModifyTableState);
  	mtstate->ps.plan = (Plan *) node;
  	mtstate->ps.state = estate;
  	mtstate->ps.targetlist = NIL;		/* not actually used */
  
  	mtstate->operation = operation;
  	mtstate->canSetTag = node->canSetTag;
  	mtstate->mt_done = false;
  
  	mtstate->mt_plans = (PlanState **) palloc0(sizeof(PlanState *) * nplans);
  	mtstate->resultRelInfo = estate->es_result_relations + node->resultRelIndex;
  	mtstate->mt_arowmarks = (List **) palloc0(sizeof(List *) * nplans);
  	mtstate->mt_nplans = nplans;
  
  	/* set up epqstate with dummy subplan data for the moment */
  	EvalPlanQualInit(&mtstate->mt_epqstate, estate, NULL, NIL, node->epqParam);
  	mtstate->fireBSTriggers = true;
  
  	/*
  	 * call ExecInitNode on each of the plans to be executed and save the
  	 * results into the array "mt_plans".  This is also a convenient place to
  	 * verify that the proposed target relations are valid and open their
  	 * indexes for insertion of new index entries.  Note we *must* set
  	 * estate->es_result_relation_info correctly while we initialize each
  	 * sub-plan; ExecContextForcesOids depends on that!
  	 */
  	saved_resultRelInfo = estate->es_result_relation_info;
  
  	resultRelInfo = mtstate->resultRelInfo;
  	i = 0;
  	foreach(l, node->plans)
  	{
  		subplan = (Plan *) lfirst(l);
  
  		/*
  		 * Verify result relation is a valid target for the current operation
  		 */
  		CheckValidResultRel(resultRelInfo->ri_RelationDesc, operation);
  
  		/*
  		 * If there are indices on the result relation, open them and save
  		 * descriptors in the result relation info, so that we can add new
  		 * index entries for the tuples we add/update.  We need not do this
  		 * for a DELETE, however, since deletion doesn't affect indexes. Also,
  		 * inside an EvalPlanQual operation, the indexes might be open
  		 * already, since we share the resultrel state with the original
  		 * query.
  		 */
  		if (resultRelInfo->ri_RelationDesc->rd_rel->relhasindex &&
  			operation != CMD_DELETE &&
  			resultRelInfo->ri_IndexRelationDescs == NULL)
  			ExecOpenIndices(resultRelInfo);
  
  		/* Now init the plan for this result rel */
  		estate->es_result_relation_info = resultRelInfo;
  		mtstate->mt_plans[i] = ExecInitNode(subplan, estate, eflags);
  
  		resultRelInfo++;
  		i++;
  	}
  
  	estate->es_result_relation_info = saved_resultRelInfo;
  
  	/*
  	 * Initialize RETURNING projections if needed.
  	 */
  	if (node->returningLists)
  	{
  		TupleTableSlot *slot;
  		ExprContext *econtext;
  
  		/*
  		 * Initialize result tuple slot and assign its rowtype using the first
  		 * RETURNING list.  We assume the rest will look the same.
  		 */
  		tupDesc = ExecTypeFromTL((List *) linitial(node->returningLists),
  								 false);
  
  		/* Set up a slot for the output of the RETURNING projection(s) */
  		ExecInitResultTupleSlot(estate, &mtstate->ps);
  		ExecAssignResultType(&mtstate->ps, tupDesc);
  		slot = mtstate->ps.ps_ResultTupleSlot;
  
  		/* Need an econtext too */
  		econtext = CreateExprContext(estate);
  		mtstate->ps.ps_ExprContext = econtext;
  
  		/*
  		 * Build a projection for each result rel.
  		 */
  		resultRelInfo = mtstate->resultRelInfo;
  		foreach(l, node->returningLists)
  		{
  			List	   *rlist = (List *) lfirst(l);
  			List	   *rliststate;
  
  			rliststate = (List *) ExecInitExpr((Expr *) rlist, &mtstate->ps);
  			resultRelInfo->ri_projectReturning =
  				ExecBuildProjectionInfo(rliststate, econtext, slot,
  									 resultRelInfo->ri_RelationDesc->rd_att);
  			resultRelInfo++;
  		}
  	}
  	else
  	{
  		/*
  		 * We still must construct a dummy result tuple type, because InitPlan
  		 * expects one (maybe should change that?).
  		 */
  		tupDesc = ExecTypeFromTL(NIL, false);
  		ExecInitResultTupleSlot(estate, &mtstate->ps);
  		ExecAssignResultType(&mtstate->ps, tupDesc);
  
  		mtstate->ps.ps_ExprContext = NULL;
  	}
  
  	/*
  	 * If we have any secondary relations in an UPDATE or DELETE, they need to
  	 * be treated like non-locked relations in SELECT FOR UPDATE, ie, the
  	 * EvalPlanQual mechanism needs to be told about them.  Locate the
  	 * relevant ExecRowMarks.
  	 */
  	foreach(l, node->rowMarks)
  	{
  		PlanRowMark *rc = (PlanRowMark *) lfirst(l);
  		ExecRowMark *erm;
  
  		Assert(IsA(rc, PlanRowMark));
  
  		/* ignore "parent" rowmarks; they are irrelevant at runtime */
  		if (rc->isParent)
  			continue;
  
  		/* find ExecRowMark (same for all subplans) */
  		erm = ExecFindRowMark(estate, rc->rti);
  
  		/* build ExecAuxRowMark for each subplan */
  		for (i = 0; i < nplans; i++)
  		{
  			ExecAuxRowMark *aerm;
  
  			subplan = mtstate->mt_plans[i]->plan;
  			aerm = ExecBuildAuxRowMark(erm, subplan->targetlist);
  			mtstate->mt_arowmarks[i] = lappend(mtstate->mt_arowmarks[i], aerm);
  		}
  	}
  
  	/* select first subplan */
  	mtstate->mt_whichplan = 0;
  	subplan = (Plan *) linitial(node->plans);
  	EvalPlanQualSetPlan(&mtstate->mt_epqstate, subplan,
  						mtstate->mt_arowmarks[0]);
  
  	/*
  	 * Initialize the junk filter(s) if needed.  INSERT queries need a filter
  	 * if there are any junk attrs in the tlist.  UPDATE and DELETE always
  	 * need a filter, since there's always a junk 'ctid' or 'wholerow'
  	 * attribute present --- no need to look first.
  	 *
  	 * If there are multiple result relations, each one needs its own junk
  	 * filter.  Note multiple rels are only possible for UPDATE/DELETE, so we
  	 * can't be fooled by some needing a filter and some not.
  	 *
  	 * This section of code is also a convenient place to verify that the
  	 * output of an INSERT or UPDATE matches the target table(s).
  	 */
  	{
  		bool		junk_filter_needed = false;
  
  		switch (operation)
  		{
  			case CMD_INSERT:
  				foreach(l, subplan->targetlist)
  				{
  					TargetEntry *tle = (TargetEntry *) lfirst(l);
  
  					if (tle->resjunk)
  					{
  						junk_filter_needed = true;
  						break;
  					}
  				}
  				break;
  			case CMD_UPDATE:
  			case CMD_DELETE:
  				junk_filter_needed = true;
  				break;
  			default:
  				elog(ERROR, "unknown operation");
  				break;
  		}
  
  		if (junk_filter_needed)
  		{
  			resultRelInfo = mtstate->resultRelInfo;
  			for (i = 0; i < nplans; i++)
  			{
  				JunkFilter *j;
  
  				subplan = mtstate->mt_plans[i]->plan;
  				if (operation == CMD_INSERT || operation == CMD_UPDATE)
  					ExecCheckPlanOutput(resultRelInfo->ri_RelationDesc,
  										subplan->targetlist);
  
  				j = ExecInitJunkFilter(subplan->targetlist,
  							resultRelInfo->ri_RelationDesc->rd_att->tdhasoid,
  									   ExecInitExtraTupleSlot(estate));
  
  				if (operation == CMD_UPDATE || operation == CMD_DELETE)
  				{
  					/* For UPDATE/DELETE, find the appropriate junk attr now */
  					if (resultRelInfo->ri_RelationDesc->rd_rel->relkind == RELKIND_RELATION)
  					{
  						j->jf_junkAttNo = ExecFindJunkAttribute(j, "ctid");
  						if (!AttributeNumberIsValid(j->jf_junkAttNo))
  							elog(ERROR, "could not find junk ctid column");
  					}
  					else
  					{
  						j->jf_junkAttNo = ExecFindJunkAttribute(j, "wholerow");
  						if (!AttributeNumberIsValid(j->jf_junkAttNo))
  							elog(ERROR, "could not find junk wholerow column");
  					}
  				}
  
  				resultRelInfo->ri_junkFilter = j;
  				resultRelInfo++;
  			}
  		}
  		else
  		{
  			if (operation == CMD_INSERT)
  				ExecCheckPlanOutput(mtstate->resultRelInfo->ri_RelationDesc,
  									subplan->targetlist);
  		}
  	}
  
  	/*
  	 * Set up a tuple table slot for use for trigger output tuples. In a plan
  	 * containing multiple ModifyTable nodes, all can share one such slot, so
  	 * we keep it in the estate.
  	 */
  	if (estate->es_trig_tuple_slot == NULL)
  		estate->es_trig_tuple_slot = ExecInitExtraTupleSlot(estate);
  
  	/*
  	 * Lastly, if this is not the primary (canSetTag) ModifyTable node, add it
  	 * to estate->es_auxmodifytables so that it will be run to completion by
  	 * ExecPostprocessPlan.  (It'd actually work fine to add the primary
  	 * ModifyTable node too, but there's no need.)  Note the use of lcons not
  	 * lappend: we need later-initialized ModifyTable nodes to be shut down
  	 * before earlier ones.  This ensures that we don't throw away RETURNING
  	 * rows that need to be seen by a later CTE subplan.
  	 */
  	if (!mtstate->canSetTag)
  		estate->es_auxmodifytables = lcons(mtstate,
  										   estate->es_auxmodifytables);
  
  	return mtstate;
  }
  
  /* ----------------------------------------------------------------
   *		ExecEndModifyTable
   *
   *		Shuts down the plan.
   *
   *		Returns nothing of interest.
   * ----------------------------------------------------------------
   */
  void
  ExecEndModifyTable(ModifyTableState *node)
  {
  	int			i;
  
  	/*
  	 * Free the exprcontext
  	 */
  	ExecFreeExprContext(&node->ps);
  
  	/*
  	 * clean out the tuple table
  	 */
  	ExecClearTuple(node->ps.ps_ResultTupleSlot);
  
  	/*
  	 * Terminate EPQ execution if active
  	 */
  	EvalPlanQualEnd(&node->mt_epqstate);
  
  	/*
  	 * shut down subplans
  	 */
  	for (i = 0; i < node->mt_nplans; i++)
  		ExecEndNode(node->mt_plans[i]);
  }
  
  void
  ExecReScanModifyTable(ModifyTableState *node)
  {
  	/*
  	 * Currently, we don't need to support rescan on ModifyTable nodes. The
  	 * semantics of that would be a bit debatable anyway.
  	 */
  	elog(ERROR, "ExecReScanModifyTable is not implemented");
  }
  