Support data-modifying commands (INSERT/UPDATE/DELETE) in WITH.

This patch implements data-modifying WITH queries according to the
semantics that the updates all happen with the same command counter value,
and in an unspecified order.  Therefore one WITH clause can't see the
effects of another, nor can the outer query see the effects other than
through the RETURNING values.  And attempts to do conflicting updates will
have unpredictable results.  We'll need to document all that.

This commit just fixes the code; documentation updates are waiting on
author.

Marko Tiikkaja and Hitoshi Harada

1 files changed, 111 insertions, 44 deletions

diff --git a/src/backend/executor/execMain.c b/src/backend/executor/execMain.c
index 68509fbfc6e..845fac1ae1c 100644
--- a/src/backend/executor/execMain.c
+++ b/src/backend/executor/execMain.c
@@ -68,6 +68,7 @@ ExecutorCheckPerms_hook_type ExecutorCheckPerms_hook = NULL;
 
 /* decls for local routines only used within this module */
 static void InitPlan(QueryDesc *queryDesc, int eflags);
+static void ExecPostprocessPlan(EState *estate);
 static void ExecEndPlan(PlanState *planstate, EState *estate);
 static void ExecutePlan(EState *estate, PlanState *planstate,
 			CmdType operation,
@@ -161,9 +162,13 @@ standard_ExecutorStart(QueryDesc *queryDesc, int eflags)
 	switch (queryDesc->operation)
 	{
 		case CMD_SELECT:
-			/* SELECT INTO and SELECT FOR UPDATE/SHARE need to mark tuples */
+			/*
+			 * SELECT INTO, SELECT FOR UPDATE/SHARE and modifying CTEs need to
+			 * mark tuples
+			 */
 			if (queryDesc->plannedstmt->intoClause != NULL ||
-				queryDesc->plannedstmt->rowMarks != NIL)
+				queryDesc->plannedstmt->rowMarks != NIL ||
+				queryDesc->plannedstmt->hasModifyingCTE)
 				estate->es_output_cid = GetCurrentCommandId(true);
 			break;
 
@@ -307,13 +312,19 @@ standard_ExecutorRun(QueryDesc *queryDesc,
  *
  *		We provide a function hook variable that lets loadable plugins
  *		get control when ExecutorEnd is called.  Such a plugin would
- *		normally call standard_ExecutorEnd().
+ *		normally call standard_ExecutorEnd().  Because such hooks expect
+ *		to execute after all plan execution is done, we run
+ *		ExecPostprocessPlan before invoking the hook.
  *
  * ----------------------------------------------------------------
  */
 void
 ExecutorEnd(QueryDesc *queryDesc)
 {
+	/* Let plan nodes do any final processing required */
+	ExecPostprocessPlan(queryDesc->estate);
+
+	/* Now close down */
 	if (ExecutorEnd_hook)
 		(*ExecutorEnd_hook) (queryDesc);
 	else
@@ -681,7 +692,6 @@ InitPlan(QueryDesc *queryDesc, int eflags)
 			InitResultRelInfo(resultRelInfo,
 							  resultRelation,
 							  resultRelationIndex,
-							  operation,
 							  estate->es_instrument);
 			resultRelInfo++;
 		}
@@ -873,24 +883,18 @@ InitPlan(QueryDesc *queryDesc, int eflags)
 }
 
 /*
- * Initialize ResultRelInfo data for one result relation
+ * Check that a proposed result relation is a legal target for the operation
+ *
+ * In most cases parser and/or planner should have noticed this already, but
+ * let's make sure.  In the view case we do need a test here, because if the
+ * view wasn't rewritten by a rule, it had better have an INSTEAD trigger.
  */
 void
-InitResultRelInfo(ResultRelInfo *resultRelInfo,
-				  Relation resultRelationDesc,
-				  Index resultRelationIndex,
-				  CmdType operation,
-				  int instrument_options)
+CheckValidResultRel(Relation resultRel, CmdType operation)
 {
-	TriggerDesc	*trigDesc = resultRelationDesc->trigdesc;
+	TriggerDesc	*trigDesc = resultRel->trigdesc;
 
-	/*
-	 * Check valid relkind ... in most cases parser and/or planner should have
-	 * noticed this already, but let's make sure.  In the view case we do need
-	 * a test here, because if the view wasn't rewritten by a rule, it had
-	 * better have an INSTEAD trigger.
-	 */
-	switch (resultRelationDesc->rd_rel->relkind)
+	switch (resultRel->rd_rel->relkind)
 	{
 		case RELKIND_RELATION:
 			/* OK */
@@ -899,13 +903,13 @@ InitResultRelInfo(ResultRelInfo *resultRelInfo,
 			ereport(ERROR,
 					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
 					 errmsg("cannot change sequence \"%s\"",
-							RelationGetRelationName(resultRelationDesc))));
+							RelationGetRelationName(resultRel))));
 			break;
 		case RELKIND_TOASTVALUE:
 			ereport(ERROR,
 					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
 					 errmsg("cannot change TOAST relation \"%s\"",
-							RelationGetRelationName(resultRelationDesc))));
+							RelationGetRelationName(resultRel))));
 			break;
 		case RELKIND_VIEW:
 			switch (operation)
@@ -915,7 +919,7 @@ InitResultRelInfo(ResultRelInfo *resultRelInfo,
 						ereport(ERROR,
 								(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
 								 errmsg("cannot insert into view \"%s\"",
-										RelationGetRelationName(resultRelationDesc)),
+										RelationGetRelationName(resultRel)),
 								 errhint("You need an unconditional ON INSERT DO INSTEAD rule or an INSTEAD OF INSERT trigger.")));
 					break;
 				case CMD_UPDATE:
@@ -923,7 +927,7 @@ InitResultRelInfo(ResultRelInfo *resultRelInfo,
 						ereport(ERROR,
 								(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
 								 errmsg("cannot update view \"%s\"",
-										RelationGetRelationName(resultRelationDesc)),
+										RelationGetRelationName(resultRel)),
 								 errhint("You need an unconditional ON UPDATE DO INSTEAD rule or an INSTEAD OF UPDATE trigger.")));
 					break;
 				case CMD_DELETE:
@@ -931,7 +935,7 @@ InitResultRelInfo(ResultRelInfo *resultRelInfo,
 						ereport(ERROR,
 								(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
 								 errmsg("cannot delete from view \"%s\"",
-										RelationGetRelationName(resultRelationDesc)),
+										RelationGetRelationName(resultRel)),
 								 errhint("You need an unconditional ON DELETE DO INSTEAD rule or an INSTEAD OF DELETE trigger.")));
 					break;
 				default:
@@ -943,17 +947,30 @@ InitResultRelInfo(ResultRelInfo *resultRelInfo,
 			ereport(ERROR,
 					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
 					 errmsg("cannot change foreign table \"%s\"",
-							RelationGetRelationName(resultRelationDesc))));
+							RelationGetRelationName(resultRel))));
 			break;
 		default:
 			ereport(ERROR,
 					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
 					 errmsg("cannot change relation \"%s\"",
-							RelationGetRelationName(resultRelationDesc))));
+							RelationGetRelationName(resultRel))));
 			break;
 	}
+}
 
-	/* OK, fill in the node */
+/*
+ * 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,
+				  int instrument_options)
+{
 	MemSet(resultRelInfo, 0, sizeof(ResultRelInfo));
 	resultRelInfo->type = T_ResultRelInfo;
 	resultRelInfo->ri_RangeTableIndex = resultRelationIndex;
@@ -962,7 +979,7 @@ InitResultRelInfo(ResultRelInfo *resultRelInfo,
 	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(trigDesc);
+	resultRelInfo->ri_TrigDesc = CopyTriggerDesc(resultRelationDesc->trigdesc);
 	if (resultRelInfo->ri_TrigDesc)
 	{
 		int			n = resultRelInfo->ri_TrigDesc->numtriggers;
@@ -983,16 +1000,6 @@ InitResultRelInfo(ResultRelInfo *resultRelInfo,
 	resultRelInfo->ri_ConstraintExprs = NULL;
 	resultRelInfo->ri_junkFilter = NULL;
 	resultRelInfo->ri_projectReturning = NULL;
-
-	/*
-	 * If there are indices on the result relation, open them and save
-	 * descriptors in the result relation info, so that we can add new index
-	 * entries for the tuples we add/update.  We need not do this for a
-	 * DELETE, however, since deletion doesn't affect indexes.
-	 */
-	if (resultRelationDesc->rd_rel->relhasindex &&
-		operation != CMD_DELETE)
-		ExecOpenIndices(resultRelInfo);
 }
 
 /*
@@ -1042,26 +1049,29 @@ ExecGetTriggerResultRel(EState *estate, Oid relid)
 	/*
 	 * 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.
+	 * 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.  Currently, we don't need any
-	 * index information in ResultRelInfos used only for triggers, so tell
-	 * InitResultRelInfo it's a DELETE.
+	 * Make the new entry in the right context.
 	 */
 	oldcontext = MemoryContextSwitchTo(estate->es_query_cxt);
 	rInfo = makeNode(ResultRelInfo);
 	InitResultRelInfo(rInfo,
 					  rel,
 					  0,		/* dummy rangetable index */
-					  CMD_DELETE,
 					  estate->es_instrument);
 	estate->es_trig_target_relations =
 		lappend(estate->es_trig_target_relations, rInfo);
 	MemoryContextSwitchTo(oldcontext);
 
+	/*
+	 * Currently, we don't need any index information in ResultRelInfos used
+	 * only for triggers, so no need to call ExecOpenIndices.
+	 */
+
 	return rInfo;
 }
 
@@ -1123,6 +1133,54 @@ ExecContextForcesOids(PlanState *planstate, bool *hasoids)
 }
 
 /* ----------------------------------------------------------------
+ *		ExecPostprocessPlan
+ *
+ *		Give plan nodes a final chance to execute before shutdown
+ * ----------------------------------------------------------------
+ */
+static void
+ExecPostprocessPlan(EState *estate)
+{
+	MemoryContext oldcontext;
+	ListCell   *lc;
+
+	/*
+	 * Switch into per-query memory context
+	 */
+	oldcontext = MemoryContextSwitchTo(estate->es_query_cxt);
+
+	/*
+	 * 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;
+		}
+	}
+
+	MemoryContextSwitchTo(oldcontext);
+}
+
+/* ----------------------------------------------------------------
  *		ExecEndPlan
  *
  *		Cleans up the query plan -- closes files and frees up storage
@@ -2026,6 +2084,7 @@ EvalPlanQualStart(EPQState *epqstate, EState *parentestate, Plan *planTree)
 	estate->es_instrument = parentestate->es_instrument;
 	estate->es_select_into = parentestate->es_select_into;
 	estate->es_into_oids = parentestate->es_into_oids;
+	estate->es_auxmodifytables = NIL;
 
 	/*
 	 * The external param list is simply shared from parent.  The internal
@@ -2080,7 +2139,11 @@ EvalPlanQualStart(EPQState *epqstate, EState *parentestate, Plan *planTree)
 	 * 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.
+	 * all.  (However, if the subplan is headed by a ModifyTable node, then
+	 * it must be a data-modifying CTE, which we will certainly not need to
+	 * re-run, so we can skip initializing it.  This is just an efficiency
+	 * hack; it won't skip data-modifying CTEs for which the ModifyTable node
+	 * is not at the top.)
 	 */
 	Assert(estate->es_subplanstates == NIL);
 	foreach(l, parentestate->es_plannedstmt->subplans)
@@ -2088,7 +2151,11 @@ EvalPlanQualStart(EPQState *epqstate, EState *parentestate, Plan *planTree)
 		Plan	   *subplan = (Plan *) lfirst(l);
 		PlanState  *subplanstate;
 
-		subplanstate = ExecInitNode(subplan, estate, 0);
+		/* Don't initialize ModifyTable subplans, per comment above */
+		if (IsA(subplan, ModifyTable))
+			subplanstate = NULL;
+		else
+			subplanstate = ExecInitNode(subplan, estate, 0);
 
 		estate->es_subplanstates = lappend(estate->es_subplanstates,
 										   subplanstate);