Create ResultRelInfos later in InitPlan, index them by RT index.

Instead of allocating all the ResultRelInfos upfront in one big array,
allocate them in ExecInitModifyTable(). es_result_relations is now an
array of ResultRelInfo pointers, rather than an array of structs, and it
is indexed by the RT index.

This simplifies things: we get rid of the separate concept of a "result
rel index", and don't need to set it in setrefs.c anymore. This also
allows follow-up optimizations (not included in this commit yet) to skip
initializing ResultRelInfos for target relations that were not needed at
runtime, and removal of the es_result_relation_info pointer.

The EState arrays of regular result rels and root result rels are merged
into one array. Similarly, the resultRelations and rootResultRelations
lists in PlannedStmt are merged into one. It's not actually clear to me
why they were kept separate in the first place, but now that the
es_result_relations array is indexed by RT index, it certainly seems
pointless.

The PlannedStmt->resultRelations list is now only needed for
ExecRelationIsTargetRelation(). One visible effect of this change is that
ExecRelationIsTargetRelation() will now return 'true' also for the
partition root, if a partitioned table is updated. That seems like a good
thing, although the function isn't used in core code, and I don't see any
reason for an FDW to call it on a partition root.

Author: Amit Langote
Discussion: https://www.postgresql.org/message-id/CA%2BHiwqGEmiib8FLiHMhKB%2BCH5dRgHSLc5N5wnvc4kym%2BZYpQEQ%40mail.gmail.com

Author: hlinnaka

src/backend/commands/copy.c

@@ -2727,6 +2727,7 @@ CopyFrom(CopyState cstate)
 	bool		leafpart_use_multi_insert = false;
 
 	Assert(cstate->rel);
+	Assert(list_length(cstate->range_table) == 1);
 
 	/*
 	 * The target must be a plain, foreign, or partitioned relation, or have
@@ -2829,25 +2830,17 @@ CopyFrom(CopyState cstate)
 	 * index-entry-making machinery.  (There used to be a huge amount of code
 	 * here that basically duplicated execUtils.c ...)
 	 */
-	resultRelInfo = makeNode(ResultRelInfo);
-	InitResultRelInfo(resultRelInfo,
-					  cstate->rel,
-					  1,		/* must match rel's position in range_table */
-					  NULL,
-					  0);
-	target_resultRelInfo = resultRelInfo;
+	ExecInitRangeTable(estate, cstate->range_table);
+	resultRelInfo = target_resultRelInfo = makeNode(ResultRelInfo);
+	ExecInitResultRelation(estate, resultRelInfo, 1);
 
 	/* Verify the named relation is a valid target for INSERT */
 	CheckValidResultRel(resultRelInfo, CMD_INSERT);
 
 	ExecOpenIndices(resultRelInfo, false);
 
-	estate->es_result_relations = resultRelInfo;
-	estate->es_num_result_relations = 1;
 	estate->es_result_relation_info = resultRelInfo;
 
-	ExecInitRangeTable(estate, cstate->range_table);
-
 	/*
 	 * Set up a ModifyTableState so we can let FDW(s) init themselves for
 	 * foreign-table result relation(s).
@@ -2856,7 +2849,7 @@ CopyFrom(CopyState cstate)
 	mtstate->ps.plan = NULL;
 	mtstate->ps.state = estate;
 	mtstate->operation = CMD_INSERT;
-	mtstate->resultRelInfo = estate->es_result_relations;
+	mtstate->resultRelInfo = resultRelInfo;
 
 	if (resultRelInfo->ri_FdwRoutine != NULL &&
 		resultRelInfo->ri_FdwRoutine->BeginForeignInsert != NULL)
@@ -3359,14 +3352,13 @@ CopyFrom(CopyState cstate)
 	if (insertMethod != CIM_SINGLE)
 		CopyMultiInsertInfoCleanup(&multiInsertInfo);
 
-	ExecCloseIndices(target_resultRelInfo);
-
 	/* Close all the partitioned tables, leaf partitions, and their indices */
 	if (proute)
 		ExecCleanupTupleRouting(mtstate, proute);
 
-	/* Close any trigger target relations */
-	ExecCleanUpTriggerState(estate);
+	/* Close the result relations, including any trigger target relations */
+	ExecCloseResultRelations(estate);
+	ExecCloseRangeTableRelations(estate);
 
 	FreeExecutorState(estate);
 

src/backend/commands/explain.c

@@ -769,27 +769,24 @@ ExplainPrintTriggers(ExplainState *es, QueryDesc *queryDesc)
 {
 	ResultRelInfo *rInfo;
 	bool		show_relname;
-	int			numrels = queryDesc->estate->es_num_result_relations;
-	int			numrootrels = queryDesc->estate->es_num_root_result_relations;
+	List	   *resultrels;
 	List	   *routerels;
 	List	   *targrels;
-	int			nr;
 	ListCell   *l;
 
+	resultrels = queryDesc->estate->es_opened_result_relations;
 	routerels = queryDesc->estate->es_tuple_routing_result_relations;
 	targrels = queryDesc->estate->es_trig_target_relations;
 
 	ExplainOpenGroup("Triggers", "Triggers", false, es);
 
-	show_relname = (numrels > 1 || numrootrels > 0 ||
+	show_relname = (list_length(resultrels) > 1 ||
 					routerels != NIL || targrels != NIL);
-	rInfo = queryDesc->estate->es_result_relations;
-	for (nr = 0; nr < numrels; rInfo++, nr++)
-		report_triggers(rInfo, show_relname, es);
-
-	rInfo = queryDesc->estate->es_root_result_relations;
-	for (nr = 0; nr < numrootrels; rInfo++, nr++)
+	foreach(l, resultrels)
+	{
+		rInfo = (ResultRelInfo *) lfirst(l);
 		report_triggers(rInfo, show_relname, es);
+	}
 
 	foreach(l, routerels)
 	{

src/backend/commands/tablecmds.c

@@ -1787,6 +1787,11 @@ ExecuteTruncateGuts(List *explicit_rels, List *relids, List *relids_logged,
 	/*
 	 * To fire triggers, we'll need an EState as well as a ResultRelInfo for
 	 * each relation.  We don't need to call ExecOpenIndices, though.
+	 *
+	 * We put the ResultRelInfos in the es_opened_result_relations list, even
+	 * though we don't have a range table and don't populate the
+	 * es_result_relations array.  That's a big bogus, but it's enough to make
+	 * ExecGetTriggerResultRel() find them.
 	 */
 	estate = CreateExecutorState();
 	resultRelInfos = (ResultRelInfo *)
@@ -1801,10 +1806,10 @@ ExecuteTruncateGuts(List *explicit_rels, List *relids, List *relids_logged,
 						  0,	/* dummy rangetable index */
 						  NULL,
 						  0);
+		estate->es_opened_result_relations =
+			lappend(estate->es_opened_result_relations, resultRelInfo);
 		resultRelInfo++;
 	}
-	estate->es_result_relations = resultRelInfos;
-	estate->es_num_result_relations = list_length(rels);
 
 	/*
 	 * Process all BEFORE STATEMENT TRUNCATE triggers before we begin

src/backend/commands/trigger.c

@@ -4227,7 +4227,7 @@ afterTriggerInvokeEvents(AfterTriggerEventList *events,
 
 	if (local_estate)
 	{
-		ExecCleanUpTriggerState(estate);
+		ExecCloseResultRelations(estate);
 		ExecResetTupleTable(estate->es_tupleTable, false);
 		FreeExecutorState(estate);
 	}