Move PartitioPruneInfo out of plan nodes into PlannedStmt

The planner will now add a given PartitioPruneInfo to
PlannedStmt.partPruneInfos instead of directly to the
Append/MergeAppend plan node.  What gets set instead in the
latter is an index field which points to the list element
of PlannedStmt.partPruneInfos containing the PartitioPruneInfo
belonging to the plan node.

A later commit will make AcquireExecutorLocks() do the initial
partition pruning to determine a minimal set of partitions to be
locked when validating a plan tree and it will need to consult the
PartitioPruneInfos referenced therein to do so.  It would be better
for the PartitioPruneInfos to be accessible directly than requiring
a walk of the plan tree to find them, which is easier when it can be
done by simply iterating over PlannedStmt.partPruneInfos.

Author: Amit Langote <amitlangote09@gmail.com>
Discussion: https://postgr.es/m/CA+HiwqFGkMSge6TgC9KQzde0ohpAycLQuV7ooitEEpbKB0O_mg@mail.gmail.com

src/backend/executor/execMain.c

@@ -825,6 +825,7 @@ InitPlan(QueryDesc *queryDesc, int eflags)
 	ExecInitRangeTable(estate, rangeTable);
 
 	estate->es_plannedstmt = plannedstmt;
+	estate->es_part_prune_infos = plannedstmt->partPruneInfos;
 
 	/*
 	 * Next, build the ExecRowMark array from the PlanRowMark(s), if any.

src/backend/executor/execParallel.c

@@ -183,6 +183,7 @@ ExecSerializePlan(Plan *plan, EState *estate)
 	pstmt->dependsOnRole = false;
 	pstmt->parallelModeNeeded = false;
 	pstmt->planTree = plan;
+	pstmt->partPruneInfos = estate->es_part_prune_infos;
 	pstmt->rtable = estate->es_range_table;
 	pstmt->resultRelations = NIL;
 	pstmt->appendRelations = NIL;

src/backend/executor/execPartition.c

@@ -1791,6 +1791,9 @@ adjust_partition_colnos_using_map(List *colnos, AttrMap *attrMap)
  *		Initialize data structure needed for run-time partition pruning and
  *		do initial pruning if needed
  *
+ * 'root_parent_relids' identifies the relation to which both the parent plan
+ * and the PartitionPruneInfo given by 'part_prune_index' belong.
+ *
  * On return, *initially_valid_subplans is assigned the set of indexes of
  * child subplans that must be initialized along with the parent plan node.
  * Initial pruning is performed here if needed and in that case only the
@@ -1803,11 +1806,24 @@ adjust_partition_colnos_using_map(List *colnos, AttrMap *attrMap)
 PartitionPruneState *
 ExecInitPartitionPruning(PlanState *planstate,
 						 int n_total_subplans,
-						 PartitionPruneInfo *pruneinfo,
+						 int part_prune_index,
+						 Bitmapset *root_parent_relids,
 						 Bitmapset **initially_valid_subplans)
 {
 	PartitionPruneState *prunestate;
 	EState	   *estate = planstate->state;
+	PartitionPruneInfo *pruneinfo;
+
+	/* Obtain the pruneinfo we need, and make sure it's the right one */
+	pruneinfo = list_nth(estate->es_part_prune_infos, part_prune_index);
+	if (!bms_equal(root_parent_relids, pruneinfo->root_parent_relids))
+		ereport(ERROR,
+				errcode(ERRCODE_INTERNAL_ERROR),
+				errmsg_internal("mismatching PartitionPruneInfo found at part_prune_index %d",
+								part_prune_index),
+				errdetail_internal("plan node relids %s, pruneinfo relids %s",
+								   bmsToString(root_parent_relids),
+								   bmsToString(pruneinfo->root_parent_relids)));
 
 	/* We may need an expression context to evaluate partition exprs */
 	ExecAssignExprContext(estate, planstate);

src/backend/executor/execUtils.c

@@ -119,6 +119,7 @@ CreateExecutorState(void)
 	estate->es_relations = NULL;
 	estate->es_rowmarks = NULL;
 	estate->es_plannedstmt = NULL;
+	estate->es_part_prune_infos = NIL;
 
 	estate->es_junkFilter = NULL;
 

src/backend/executor/nodeAppend.c

@@ -134,7 +134,7 @@ ExecInitAppend(Append *node, EState *estate, int eflags)
 	appendstate->as_begun = false;
 
 	/* If run-time partition pruning is enabled, then set that up now */
-	if (node->part_prune_info != NULL)
+	if (node->part_prune_index >= 0)
 	{
 		PartitionPruneState *prunestate;
 
@@ -145,7 +145,8 @@ ExecInitAppend(Append *node, EState *estate, int eflags)
 		 */
 		prunestate = ExecInitPartitionPruning(&appendstate->ps,
 											  list_length(node->appendplans),
-											  node->part_prune_info,
+											  node->part_prune_index,
+											  node->apprelids,
 											  &validsubplans);
 		appendstate->as_prune_state = prunestate;
 		nplans = bms_num_members(validsubplans);

src/backend/executor/nodeMergeAppend.c

@@ -82,7 +82,7 @@ ExecInitMergeAppend(MergeAppend *node, EState *estate, int eflags)
 	mergestate->ps.ExecProcNode = ExecMergeAppend;
 
 	/* If run-time partition pruning is enabled, then set that up now */
-	if (node->part_prune_info != NULL)
+	if (node->part_prune_index >= 0)
 	{
 		PartitionPruneState *prunestate;
 
@@ -93,7 +93,8 @@ ExecInitMergeAppend(MergeAppend *node, EState *estate, int eflags)
 		 */
 		prunestate = ExecInitPartitionPruning(&mergestate->ps,
 											  list_length(node->mergeplans),
-											  node->part_prune_info,
+											  node->part_prune_index,
+											  node->apprelids,
 											  &validsubplans);
 		mergestate->ms_prune_state = prunestate;
 		nplans = bms_num_members(validsubplans);