For partitionwise join, match on partcollation, not parttypcoll.

The previous code considered two tables to have the partition scheme
if the underlying columns had the same collation, but what we
actually need to compare is not the collations associated with the
column but the collation used for partitioning.  Fix that.

Robert Haas and Amit Langote

Discussion: http://postgr.es/m/0f95f924-0efa-4cf5-eb5f-9a3d1bc3c33d@lab.ntt.co.jp

src/backend/optimizer/util/plancat.c

@@ -1891,7 +1891,7 @@ find_partition_scheme(PlannerInfo *root, Relation relation)
 				   sizeof(Oid) * partnatts) != 0 ||
 			memcmp(partkey->partopcintype, part_scheme->partopcintype,
 				   sizeof(Oid) * partnatts) != 0 ||
-			memcmp(partkey->parttypcoll, part_scheme->parttypcoll,
+			memcmp(partkey->partcollation, part_scheme->partcollation,
 				   sizeof(Oid) * partnatts) != 0)
 			continue;
 
@@ -1926,8 +1926,8 @@ find_partition_scheme(PlannerInfo *root, Relation relation)
 	memcpy(part_scheme->partopcintype, partkey->partopcintype,
 		   sizeof(Oid) * partnatts);
 
-	part_scheme->parttypcoll = (Oid *) palloc(sizeof(Oid) * partnatts);
-	memcpy(part_scheme->parttypcoll, partkey->parttypcoll,
+	part_scheme->partcollation = (Oid *) palloc(sizeof(Oid) * partnatts);
+	memcpy(part_scheme->partcollation, partkey->partcollation,
 		   sizeof(Oid) * partnatts);
 
 	part_scheme->parttyplen = (int16 *) palloc(sizeof(int16) * partnatts);

src/include/nodes/relation.h

@@ -351,7 +351,7 @@ typedef struct PartitionSchemeData
 	int16		partnatts;		/* number of partition attributes */
 	Oid		   *partopfamily;	/* OIDs of operator families */
 	Oid		   *partopcintype;	/* OIDs of opclass declared input data types */
-	Oid		   *parttypcoll;	/* OIDs of collations of partition keys. */
+	Oid		   *partcollation;	/* OIDs of partitioning collations */
 
 	/* Cached information about partition key data types. */
 	int16	   *parttyplen;