/*-------------------------------------------------------------------------
 *
 * nodeModifyTable.c
 *	  routines to handle ModifyTable nodes.
 *
 * Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *	  $PostgreSQL: pgsql/src/backend/executor/nodeModifyTable.c,v 1.9 2010/08/18 21:52:24 tgl Exp $
 *
 *-------------------------------------------------------------------------
 */
/* 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/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)
{
	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->n_before_row[TRIGGER_EVENT_INSERT] > 0)
	{
		HeapTuple	newtuple;

		newtuple = ExecBRInsertTriggers(estate, resultRelInfo, tuple);

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

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

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

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

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

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

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

	/* 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
 *
 *		Returns RETURNING result if any, otherwise NULL.
 * ----------------------------------------------------------------
 */
static TupleTableSlot *
ExecDelete(ItemPointer tupleid,
		   TupleTableSlot *planSlot,
		   EPQState *epqstate,
		   EState *estate)
{
	ResultRelInfo *resultRelInfo;
	Relation	resultRelationDesc;
	HTSU_Result result;
	ItemPointerData update_ctid;
	TransactionId update_xmax;

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

	/* BEFORE ROW DELETE Triggers */
	if (resultRelInfo->ri_TrigDesc &&
		resultRelInfo->ri_TrigDesc->n_before_row[TRIGGER_EVENT_DELETE] > 0)
	{
		bool		dodelete;

		dodelete = ExecBRDeleteTriggers(estate, epqstate, resultRelInfo,
										tupleid);

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

	/*
	 * delete the tuple
	 *
	 * Note: if es_crosscheck_snapshot isn't InvalidSnapshot, we check that
	 * the row to be deleted is visible to that snapshot, and throw a can't-
	 * serialize error if not.	This is a special-case behavior needed for
	 * referential integrity updates in serializable transactions.
	 */
ldelete:;
	result = heap_delete(resultRelationDesc, tupleid,
						 &update_ctid, &update_xmax,
						 estate->es_output_cid,
						 estate->es_crosscheck_snapshot,
						 true /* wait for commit */ );
	switch (result)
	{
		case HeapTupleSelfUpdated:
			/* already deleted by self; nothing to do */
			return NULL;

		case HeapTupleMayBeUpdated:
			break;

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

	(estate->es_processed)++;

	/*
	 * Note: Normally one would think that we have to delete index tuples
	 * associated with the heap tuple now...
	 *
	 * ... but in POSTGRES, we have no need to do this because VACUUM will
	 * take care of it later.  We can't delete index tuples immediately
	 * anyway, since the tuple is still visible to other transactions.
	 */

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

	/* Process RETURNING if present */
	if (resultRelInfo->ri_projectReturning)
	{
		/*
		 * We have to put the target tuple into a slot, which means first we
		 * gotta fetch it.	We can use the trigger tuple slot.
		 */
		TupleTableSlot *slot = estate->es_trig_tuple_slot;
		TupleTableSlot *rslot;
		HeapTupleData deltuple;
		Buffer		delbuffer;

		deltuple.t_self = *tupleid;
		if (!heap_fetch(resultRelationDesc, SnapshotAny,
						&deltuple, &delbuffer, false, NULL))
			elog(ERROR, "failed to fetch deleted tuple for DELETE RETURNING");

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

		rslot = ExecProcessReturning(resultRelInfo->ri_projectReturning,
									 slot, planSlot);

		ExecClearTuple(slot);
		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..
 *
 *		Returns RETURNING result if any, otherwise NULL.
 * ----------------------------------------------------------------
 */
static TupleTableSlot *
ExecUpdate(ItemPointer tupleid,
		   TupleTableSlot *slot,
		   TupleTableSlot *planSlot,
		   EPQState *epqstate,
		   EState *estate)
{
	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->n_before_row[TRIGGER_EVENT_UPDATE] > 0)
	{
		HeapTuple	newtuple;

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

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

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

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

	/*
	 * Check the constraints of the tuple
	 *
	 * If we generate a new candidate tuple after EvalPlanQual testing, we
	 * must loop back here and recheck constraints.  (We don't need to redo
	 * triggers, however.  If there are any BEFORE triggers then trigger.c
	 * will have done heap_lock_tuple to lock the correct tuple, so there's no
	 * need to do them again.)
	 */
lreplace:;
	if (resultRelationDesc->rd_att->constr)
		ExecConstraints(resultRelInfo, slot, estate);

	/*
	 * replace the heap tuple
	 *
	 * Note: if es_crosscheck_snapshot isn't InvalidSnapshot, we check that
	 * the row to be updated is visible to that snapshot, and throw a can't-
	 * serialize error if not.	This is a special-case behavior needed for
	 * referential integrity updates in serializable transactions.
	 */
	result = heap_update(resultRelationDesc, tupleid, tuple,
						 &update_ctid, &update_xmax,
						 estate->es_output_cid,
						 estate->es_crosscheck_snapshot,
						 true /* wait for commit */ );
	switch (result)
	{
		case HeapTupleSelfUpdated:
			/* already deleted by self; nothing to do */
			return NULL;

		case HeapTupleMayBeUpdated:
			break;

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

	(estate->es_processed)++;

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

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

	/* 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->ps.state->es_result_relations);
			break;
		case CMD_UPDATE:
			ExecBSUpdateTriggers(node->ps.state,
								 node->ps.state->es_result_relations);
			break;
		case CMD_DELETE:
			ExecBSDeleteTriggers(node->ps.state,
								 node->ps.state->es_result_relations);
			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->ps.state->es_result_relations);
			break;
		case CMD_UPDATE:
			ExecASUpdateTriggers(node->ps.state,
								 node->ps.state->es_result_relations);
			break;
		case CMD_DELETE:
			ExecASDeleteTriggers(node->ps.state,
								 node->ps.state->es_result_relations);
			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;
	PlanState  *subplanstate;
	JunkFilter *junkfilter;
	TupleTableSlot *slot;
	TupleTableSlot *planSlot;
	ItemPointer tupleid = NULL;
	ItemPointerData tuple_ctid;

	/*
	 * On first call, fire BEFORE STATEMENT triggers before proceeding.
	 */
	if (node->fireBSTriggers)
	{
		fireBSTriggers(node);
		node->fireBSTriggers = false;
	}

	/*
	 * es_result_relation_info must point to the currently active result
	 * relation.  (Note we assume that ModifyTable nodes can't be nested.) We
	 * want it to be NULL whenever we're not within ModifyTable, though.
	 */
	estate->es_result_relation_info =
		estate->es_result_relations + node->mt_whichplan;

	/* Preload local variables */
	subplanstate = node->mt_plans[node->mt_whichplan];
	junkfilter = estate->es_result_relation_info->ri_junkFilter;

	/*
	 * 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)
			{
				estate->es_result_relation_info++;
				subplanstate = node->mt_plans[node->mt_whichplan];
				junkfilter = estate->es_result_relation_info->ri_junkFilter;
				EvalPlanQualSetPlan(&node->mt_epqstate, subplanstate->plan);
				continue;
			}
			else
				break;
		}

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

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

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

				tupleid = (ItemPointer) DatumGetPointer(datum);
				tuple_ctid = *tupleid;	/* be sure we don't free the ctid!! */
				tupleid = &tuple_ctid;
			}

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

		switch (operation)
		{
			case CMD_INSERT:
				slot = ExecInsert(slot, planSlot, estate);
				break;
			case CMD_UPDATE:
				slot = ExecUpdate(tupleid, slot, planSlot,
								  &node->mt_epqstate, estate);
				break;
			case CMD_DELETE:
				slot = ExecDelete(tupleid, planSlot,
								  &node->mt_epqstate, estate);
				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 = NULL;
			return slot;
		}
	}

	/* Reset es_result_relation_info before exiting */
	estate->es_result_relation_info = NULL;

	/*
	 * We're done, but fire AFTER STATEMENT triggers before exiting.
	 */
	fireASTriggers(node);

	return NULL;
}

/* ----------------------------------------------------------------
 *		ExecInitModifyTable
 * ----------------------------------------------------------------
 */
ModifyTableState *
ExecInitModifyTable(ModifyTable *node, EState *estate, int eflags)
{
	ModifyTableState *mtstate;
	CmdType		operation = node->operation;
	int			nplans = list_length(node->plans);
	ResultRelInfo *resultRelInfo;
	TupleDesc	tupDesc;
	Plan	   *subplan;
	ListCell   *l;
	int			i;

	/* check for unsupported flags */
	Assert(!(eflags & (EXEC_FLAG_BACKWARD | EXEC_FLAG_MARK)));

	/*
	 * 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 ...
	 */
	if (estate->es_epqTuple != NULL)
		elog(ERROR, "ModifyTable should not be called during EvalPlanQual");

	/*
	 * create state structure
	 */
	mtstate = makeNode(ModifyTableState);
	mtstate->ps.plan = (Plan *) node;
	mtstate->ps.state = estate;
	mtstate->ps.targetlist = NIL;		/* not actually used */

	mtstate->mt_plans = (PlanState **) palloc0(sizeof(PlanState *) * nplans);
	mtstate->mt_nplans = nplans;
	mtstate->operation = operation;
	/* set up epqstate with dummy subplan pointer for the moment */
	EvalPlanQualInit(&mtstate->mt_epqstate, estate, NULL, node->epqParam);
	mtstate->fireBSTriggers = true;

	/* For the moment, assume our targets are exactly the global result rels */

	/*
	 * call ExecInitNode on each of the plans to be executed and save the
	 * results into the array "mt_plans".  Note we *must* set
	 * estate->es_result_relation_info correctly while we initialize each
	 * sub-plan; ExecContextForcesOids depends on that!
	 */
	estate->es_result_relation_info = estate->es_result_relations;
	i = 0;
	foreach(l, node->plans)
	{
		subplan = (Plan *) lfirst(l);
		mtstate->mt_plans[i] = ExecInitNode(subplan, estate, eflags);
		estate->es_result_relation_info++;
		i++;
	}
	estate->es_result_relation_info = NULL;

	/* select first subplan */
	mtstate->mt_whichplan = 0;
	subplan = (Plan *) linitial(node->plans);
	EvalPlanQualSetPlan(&mtstate->mt_epqstate, subplan);

	/*
	 * 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.
		 */
		Assert(list_length(node->returningLists) == estate->es_num_result_relations);
		resultRelInfo = estate->es_result_relations;
		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 = NULL;
		ListCell   *lce;

		Assert(IsA(rc, PlanRowMark));

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

		foreach(lce, estate->es_rowMarks)
		{
			erm = (ExecRowMark *) lfirst(lce);
			if (erm->rti == rc->rti)
				break;
			erm = NULL;
		}
		if (erm == NULL)
			elog(ERROR, "failed to find ExecRowMark for PlanRowMark %u",
				 rc->rti);

		EvalPlanQualAddRowMark(&mtstate->mt_epqstate, erm);
	}

	/*
	 * 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' 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 = estate->es_result_relations;
			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 ctid junk attr now */
					j->jf_junkAttNo = ExecFindJunkAttribute(j, "ctid");
					if (!AttributeNumberIsValid(j->jf_junkAttNo))
						elog(ERROR, "could not find junk ctid column");
				}

				resultRelInfo->ri_junkFilter = j;
				resultRelInfo++;
			}
		}
		else
		{
			if (operation == CMD_INSERT)
				ExecCheckPlanOutput(estate->es_result_relations->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);

	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");
}
