From 7828f62949c4d57c176059dda910ccf1f7deaf96 Mon Sep 17 00:00:00 2001
From: amit <amitlangote09@gmail.com>
Date: Fri, 22 Mar 2019 15:09:45 +0900
Subject: [PATCH v34 8/9] Rearrange the code in make_partitionedrel_pruneinfo
 for efficiency

The current code will loop over all partitions to create maps that
will be put into the PartitionedRelPruneInfo of a given partitioned
table, *before* checking if run-time pruning will be needed at all.

This commit rearranges the code such that maps are created *after*
we've determined that run-time will be needed.
---
 src/backend/partitioning/partprune.c | 84 ++++++++++++++++++++----------------
 1 file changed, 47 insertions(+), 37 deletions(-)

diff --git a/src/backend/partitioning/partprune.c b/src/backend/partitioning/partprune.c
index e766555a9f..6004ae37f3 100644
--- a/src/backend/partitioning/partprune.c
+++ b/src/backend/partitioning/partprune.c
@@ -333,39 +333,24 @@ make_partitionedrel_pruneinfo(PlannerInfo *root, RelOptInfo *parentrel,
 	 */
 	relid_subpart_map = palloc0(sizeof(int) * root->simple_rel_array_size);
 
-	/*
-	 * relid_subpart_map maps relid of a non-leaf partition to the index in
-	 * 'partitioned_rels' of that rel (which will also be the index in the
-	 * returned PartitionedRelPruneInfo list of the info for that partition).
-	 */
-	i = 1;
-	foreach(lc, partitioned_rels)
-	{
-		Index		rti = lfirst_int(lc);
-
-		Assert(rti < root->simple_rel_array_size);
-		/* No duplicates please */
-		Assert(relid_subpart_map[rti] == 0);
-
-		relid_subpart_map[rti] = i++;
-	}
-
 	/* We now build a PartitionedRelPruneInfo for each partitioned rel */
+	i = 1;
 	foreach(lc, partitioned_rels)
 	{
 		Index		rti = lfirst_int(lc);
 		RelOptInfo *subpart = find_base_rel(root, rti);
 		PartitionedRelPruneInfo *pinfo;
-		Bitmapset  *present_parts;
-		int			nparts = subpart->nparts;
 		int			partnatts = subpart->part_scheme->partnatts;
-		int		   *subplan_map;
-		int		   *subpart_map;
-		Oid		   *relid_map;
 		List	   *partprunequal;
 		List	   *pruning_steps;
 		bool		contradictory;
 
+		/* Map the table's RT index to its position in partitioned_rels. */
+		Assert(rti < root->simple_rel_array_size);
+		/* No duplicates please */
+		Assert(relid_subpart_map[rti] == 0);
+		relid_subpart_map[rti] = i++;
+
 		/*
 		 * The first item in the list is the target partitioned relation.
 		 */
@@ -429,6 +414,45 @@ make_partitionedrel_pruneinfo(PlannerInfo *root, RelOptInfo *parentrel,
 			return NIL;
 		}
 
+		/* Other information will be set in the following loop. */
+		pinfo = makeNode(PartitionedRelPruneInfo);
+		pinfo->rtindex = rti;
+		pinfo->pruning_steps = pruning_steps;
+
+		/*
+		 * Determine which pruning types should be enabled at this level.
+		 * This also records paramids relevant to pruning steps in 'pinfo'.
+		 */
+		doruntimeprune |= analyze_partkey_exprs(pinfo, pruning_steps,
+												partnatts);
+
+		pinfolist = lappend(pinfolist, pinfo);
+	}
+
+	if (!doruntimeprune)
+	{
+		/* No run-time pruning required. */
+		return NIL;
+	}
+
+	/*
+	 * Run-time pruning will be required, so initialize other information.
+	 * That includes two maps -- one needed to convert partition indexes
+	 * of leaf partitions to the indexes of their subplans in the subplan
+	 * list, another needed to convert partition indexes of sub-partitioned
+	 * partitions to the indexes of their PartitionedRelPruneInfo in the
+	 * PartitionedRelPruneInfo list.
+	 */
+	foreach(lc, pinfolist)
+	{
+		PartitionedRelPruneInfo *pinfo = lfirst(lc);
+		RelOptInfo *subpart = find_base_rel(root, pinfo->rtindex);
+		Bitmapset  *present_parts;
+		int			nparts = subpart->nparts;
+		int		   *subplan_map;
+		int		   *subpart_map;
+		Oid		   *relid_map;
+
 		/*
 		 * Construct the subplan and subpart maps for this partitioning level.
 		 * Here we convert to zero-based indexes, with -1 for empty entries.
@@ -459,30 +483,16 @@ make_partitionedrel_pruneinfo(PlannerInfo *root, RelOptInfo *parentrel,
 				subplansfound = bms_add_member(subplansfound, subplanidx);
 		}
 
-		pinfo = makeNode(PartitionedRelPruneInfo);
-		pinfo->rtindex = rti;
-		pinfo->pruning_steps = pruning_steps;
+		/* Record the maps and other information. */
 		pinfo->present_parts = present_parts;
 		pinfo->nparts = nparts;
 		pinfo->subplan_map = subplan_map;
 		pinfo->subpart_map = subpart_map;
 		pinfo->relid_map = relid_map;
-
-		/* Determine which pruning types should be enabled at this level */
-		doruntimeprune |= analyze_partkey_exprs(pinfo, pruning_steps,
-												partnatts);
-
-		pinfolist = lappend(pinfolist, pinfo);
 	}
 
 	pfree(relid_subpart_map);
 
-	if (!doruntimeprune)
-	{
-		/* No run-time pruning required. */
-		return NIL;
-	}
-
 	*matchedsubplans = subplansfound;
 
 	return pinfolist;
-- 
2.11.0