From c6f5cabbe335d7de9668f3341bebc01e74250061 Mon Sep 17 00:00:00 2001
From: Metin Doslu <metin@citusdata.com>
Date: Wed, 26 Oct 2016 18:39:53 +0300
Subject: [PATCH] Error on different shard placement count

In ErrorIfShardPlacementsNotColocated(), while checking if shards are colocated,
error out if matching shard intervals have different number of shard placements.
---
 src/backend/distributed/utils/colocation_utils.c  | 15 +++++++++++++--
 .../regress/expected/multi_colocation_utils.out   |  2 +-
 2 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/src/backend/distributed/utils/colocation_utils.c b/src/backend/distributed/utils/colocation_utils.c
index 11060526f..432fedd27 100644
--- a/src/backend/distributed/utils/colocation_utils.c
+++ b/src/backend/distributed/utils/colocation_utils.c
@@ -151,8 +151,9 @@ MarkTablesColocated(Oid sourceRelationId, Oid targetRelationId)
  * following cases:
  * 1.Shard counts are different,
  * 2.Shard intervals don't match
- * 3.Shard placements are not colocated (not on the same node)
- * 4.Shard placements have different health states
+ * 3.Matching shard intervals have different number of shard placements
+ * 4.Shard placements are not colocated (not on the same node)
+ * 5.Shard placements have different health states
  *
  * Note that, this functions assumes that both tables are hash distributed.
  */
@@ -219,6 +220,16 @@ ErrorIfShardPlacementsNotColocated(Oid leftRelationId, Oid rightRelationId)
 		leftPlacementList = ShardPlacementList(leftShardId);
 		rightPlacementList = ShardPlacementList(rightShardId);
 
+		if (list_length(leftPlacementList) != list_length(rightPlacementList))
+		{
+			ereport(ERROR, (errmsg("cannot colocate tables %s and %s",
+								   leftRelationName, rightRelationName),
+							errdetail("Shard %ld of %s and shard %ld of %s "
+									  "have different number of shard placements.",
+									  leftShardId, leftRelationName,
+									  rightShardId, rightRelationName)));
+		}
+
 		/* sort shard placements according to the node */
 		sortedLeftPlacementList = SortList(leftPlacementList,
 										   CompareShardPlacementsByNode);
diff --git a/src/test/regress/expected/multi_colocation_utils.out b/src/test/regress/expected/multi_colocation_utils.out
index b87eba729..7bd235aeb 100644
--- a/src/test/regress/expected/multi_colocation_utils.out
+++ b/src/test/regress/expected/multi_colocation_utils.out
@@ -689,7 +689,7 @@ ERROR:  cannot colocate tables table1_groupb and table1_groupd
 DETAIL:  Shard counts don't match for table1_groupb and table1_groupd.
 SELECT mark_tables_colocated('table1_groupB', ARRAY['table1_groupE']);
 ERROR:  cannot colocate tables table1_groupb and table1_groupe
-DETAIL:  Shard 1300027 of table1_groupb and shard 1300047 of table1_groupe are not colocated.
+DETAIL:  Shard 1300026 of table1_groupb and shard 1300046 of table1_groupe have different number of shard placements.
 SELECT mark_tables_colocated('table1_groupB', ARRAY['table1_groupF']);
 ERROR:  cannot colocate tables table1_groupb and table1_groupf
 DETAIL:  Shard counts don't match for table1_groupb and table1_groupf.