From c1fa4b9f04f328b8df54ef487ee9d46f5978e0de Mon Sep 17 00:00:00 2001
From: amit <amitlangote09@gmail.com>
Date: Mon, 26 Dec 2016 17:44:14 +0900
Subject: [PATCH] Avoid tuple coversion in common partitioning cases

Currently, the tuple conversion is performed after a tuple is routed,
even if the attributes of a target leaf partition map one-to-one with
those of the root table, which is wasteful.  Avoid that by making
convert_tuples_by_name() return a NULL map for such cases.

Reported by: n/a
Patch by: Amit Langote
Reports: n/a
---
 src/backend/access/common/tupconvert.c | 18 ++++++++++--------
 src/backend/catalog/partition.c        |  3 +--
 2 files changed, 11 insertions(+), 10 deletions(-)

diff --git a/src/backend/access/common/tupconvert.c b/src/backend/access/common/tupconvert.c
index b17ceafa6e..a4012525d8 100644
--- a/src/backend/access/common/tupconvert.c
+++ b/src/backend/access/common/tupconvert.c
@@ -138,12 +138,13 @@ convert_tuples_by_position(TupleDesc indesc,
 						   nincols, noutcols)));
 
 	/*
-	 * Check to see if the map is one-to-one and the tuple types are the same.
-	 * (We check the latter because if they're not, we want to do conversion
-	 * to inject the right OID into the tuple datum.)
+	 * Check to see if the map is one-to-one, in which case we need not do
+	 * the tuple conversion.  That's not enough though if either source or
+	 * destination (tuples) contains OIDs; we'd need conversion in that case
+	 * to inject the right OID into the tuple datum.
 	 */
 	if (indesc->natts == outdesc->natts &&
-		indesc->tdtypeid == outdesc->tdtypeid)
+		!indesc->tdhasoid && !outdesc->tdhasoid)
 	{
 		for (i = 0; i < n; i++)
 		{
@@ -214,12 +215,13 @@ convert_tuples_by_name(TupleDesc indesc,
 	attrMap = convert_tuples_by_name_map(indesc, outdesc, msg);
 
 	/*
-	 * Check to see if the map is one-to-one and the tuple types are the same.
-	 * (We check the latter because if they're not, we want to do conversion
-	 * to inject the right OID into the tuple datum.)
+	 * Check to see if the map is one-to-one, in which case we need not do
+	 * the tuple conversion.  That's not enough though if either source or
+	 * destination (tuples) contains OIDs; we'd need conversion in that case
+	 * to inject the right OID into the tuple datum.
 	 */
 	if (indesc->natts == outdesc->natts &&
-		indesc->tdtypeid == outdesc->tdtypeid)
+		!indesc->tdhasoid && !outdesc->tdhasoid)
 	{
 		same = true;
 		for (i = 0; i < n; i++)
diff --git a/src/backend/catalog/partition.c b/src/backend/catalog/partition.c
index 7be60529c5..4bcef58763 100644
--- a/src/backend/catalog/partition.c
+++ b/src/backend/catalog/partition.c
@@ -1700,12 +1700,11 @@ get_partition_for_tuple(PartitionDispatch *pd,
 			return -1;
 		}
 
-		if (myslot != NULL)
+		if (myslot != NULL && map != NULL)
 		{
 			HeapTuple	tuple = ExecFetchSlotTuple(slot);
 
 			ExecClearTuple(myslot);
-			Assert(map != NULL);
 			tuple = do_convert_tuple(tuple, map);
 			ExecStoreTuple(tuple, myslot, InvalidBuffer, true);
 			slot = myslot;
-- 
2.11.0

