From 509ffbfc54967ebac4bcd4bb70def9b657093209 Mon Sep 17 00:00:00 2001
From: Brian Cloutier <github@briancloutier.com>
Date: Mon, 4 Apr 2016 09:37:31 -0700
Subject: [PATCH] 6x improvement in planning speed with very ~large tables

---
 .../planner/multi_logical_optimizer.c         | 20 +++++++++++--------
 .../planner/multi_physical_planner.c          | 10 +++++++++-
 2 files changed, 21 insertions(+), 9 deletions(-)

diff --git a/src/backend/distributed/planner/multi_logical_optimizer.c b/src/backend/distributed/planner/multi_logical_optimizer.c
index a09e49557..744e851f6 100644
--- a/src/backend/distributed/planner/multi_logical_optimizer.c
+++ b/src/backend/distributed/planner/multi_logical_optimizer.c
@@ -139,7 +139,7 @@ static bool JoinOnPartitionColumn(Query *query);
 static void ErrorIfUnsupportedShardDistribution(Query *query);
 static List * RelationIdList(Query *query);
 static bool CoPartitionedTables(Oid firstRelationId, Oid secondRelationId);
-static bool ShardIntervalsEqual(ShardInterval *firstInterval,
+static bool ShardIntervalsEqual(FmgrInfo* comparisonFunction, ShardInterval *firstInterval,
 								ShardInterval *secondInterval);
 static void ErrorIfUnsupportedFilters(Query *subquery);
 static bool EqualOpExpressionLists(List *firstOpExpressionList,
@@ -3483,8 +3483,11 @@ RelationIdList(Query *query)
 static bool
 CoPartitionedTables(Oid firstRelationId, Oid secondRelationId)
 {
+	FmgrInfo *comparisonFunction = NULL;
 	bool coPartitionedTables = true;
 	uint32 intervalIndex = 0;
+	Oid typeId = InvalidOid;
+
 	DistTableCacheEntry *firstTableCache = DistributedTableCacheEntry(firstRelationId);
 	DistTableCacheEntry *secondTableCache = DistributedTableCacheEntry(secondRelationId);
 	ShardInterval *sortedFirstIntervalArray = firstTableCache->sortedShardIntervalArray;
@@ -3503,12 +3506,17 @@ CoPartitionedTables(Oid firstRelationId, Oid secondRelationId)
 		return true;
 	}
 
+	typeId = sortedFirstIntervalArray[0].valueTypeId;
+	comparisonFunction = GetFunctionInfo(typeId, BTREE_AM_OID, BTORDER_PROC);
+
 	for (intervalIndex = 0; intervalIndex < firstListShardCount; intervalIndex++)
 	{
 		ShardInterval *firstInterval = &sortedFirstIntervalArray[intervalIndex];
 		ShardInterval *secondInterval = &sortedSecondIntervalArray[intervalIndex];
 
-		bool shardIntervalsEqual = ShardIntervalsEqual(firstInterval, secondInterval);
+		bool shardIntervalsEqual = ShardIntervalsEqual(comparisonFunction,
+													firstInterval,
+													secondInterval);
 		if (!shardIntervalsEqual)
 		{
 			coPartitionedTables = false;
@@ -3524,19 +3532,15 @@ CoPartitionedTables(Oid firstRelationId, Oid secondRelationId)
  * ShardIntervalsEqual checks if given shard intervals have equal min/max values.
  */
 static bool
-ShardIntervalsEqual(ShardInterval *firstInterval, ShardInterval *secondInterval)
+ShardIntervalsEqual(FmgrInfo* comparisonFunction, ShardInterval *firstInterval,
+		ShardInterval *secondInterval)
 {
-	Oid typeId = InvalidOid;
-	FmgrInfo *comparisonFunction = NULL;
 	bool shardIntervalsEqual = false;
 	Datum firstMin = 0;
 	Datum firstMax = 0;
 	Datum secondMin = 0;
 	Datum secondMax = 0;
 
-	typeId = firstInterval->valueTypeId;
-	comparisonFunction = GetFunctionInfo(typeId, BTREE_AM_OID, BTORDER_PROC);
-
 	firstMin = firstInterval->minValue;
 	firstMax = firstInterval->maxValue;
 	secondMin = secondInterval->minValue;
diff --git a/src/backend/distributed/planner/multi_physical_planner.c b/src/backend/distributed/planner/multi_physical_planner.c
index ba1bd8483..47208225c 100644
--- a/src/backend/distributed/planner/multi_physical_planner.c
+++ b/src/backend/distributed/planner/multi_physical_planner.c
@@ -2003,6 +2003,7 @@ SubquerySqlTaskList(Job *job)
 	uint32 anchorRangeTableId = 0;
 	uint32 rangeTableIndex = 0;
 	const uint32 fragmentSize = sizeof(RangeTableFragment);
+	uint64 maxTableSize = 0;
 
 	/* find filters on partition columns */
 	ExtractQueryWalker((Node *) subquery, &queryList);
@@ -2026,7 +2027,6 @@ SubquerySqlTaskList(Job *job)
 
 	/* get list of all range tables in subquery tree */
 	ExtractRangeTableRelationWalker((Node *) subquery, &rangeTableList);
-	anchorRangeTableId = AnchorRangeTableId(rangeTableList);
 
 	/*
 	 * For each range table entry, first we prune shards for the relation
@@ -2045,6 +2045,7 @@ SubquerySqlTaskList(Job *job)
 		uint32 tableId = rangeTableIndex + 1; /* tableId starts from 1 */
 		uint32 finalShardCount = 0;
 		uint32 shardIndex = 0;
+		uint64 tableSize = 0;
 
 		if (opExpressionList != NIL)
 		{
@@ -2073,6 +2074,8 @@ SubquerySqlTaskList(Job *job)
 		{
 			ShardInterval *shardInterval = sortedIntervalArray[shardIndex];
 
+			tableSize += ShardLength(shardInterval->shardId);
+
 			RangeTableFragment *shardFragment = palloc0(fragmentSize);
 			shardFragment->fragmentReference = &(shardInterval->shardId);
 			shardFragment->fragmentType = CITUS_RTE_RELATION;
@@ -2094,6 +2097,11 @@ SubquerySqlTaskList(Job *job)
 			}
 		}
 
+		if (anchorRangeTableId == 0 || tableSize > maxTableSize){
+			maxTableSize = tableSize;
+			anchorRangeTableId = tableId;
+		}
+
 		rangeTableIndex++;
 	}