Ignore partitioned indexes where appropriate

get_relation_info() was too optimistic about opening indexes in
partitioned tables, which would raise errors when any queries were
planned on such tables.  Fix by ignoring any indexes of the partitioned
kind.

CLUSTER (and ALTER TABLE CLUSTER ON) had a similar problem.  Fix by
disallowing these commands in partitioned tables.

Fallout from 8b08f7d4820f.

src/backend/commands/cluster.c

@@ -128,6 +128,14 @@ cluster(ClusterStmt *stmt, bool isTopLevel)
 					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 					 errmsg("cannot cluster temporary tables of other sessions")));
 
+		/*
+		 * Reject clustering a partitioned table.
+		 */
+		if (rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
+			ereport(ERROR,
+					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+					 errmsg("cannot cluster a partitioned table")));
+
 		if (stmt->indexname == NULL)
 		{
 			ListCell   *index;
@@ -482,6 +490,12 @@ mark_index_clustered(Relation rel, Oid indexOid, bool is_internal)
 	Relation	pg_index;
 	ListCell   *index;
 
+	/* Disallow applying to a partitioned table */
+	if (rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("cannot mark index clustered in partitioned table")));
+
 	/*
 	 * If the index is already marked clustered, no need to do anything.
 	 */

src/backend/optimizer/util/plancat.c

@@ -207,6 +207,16 @@ get_relation_info(PlannerInfo *root, Oid relationObjectId, bool inhparent,
 				continue;
 			}
 
+			/*
+			 * Ignore partitioned indexes, since they are not usable for
+			 * queries.
+			 */
+			if (indexRelation->rd_rel->relkind == RELKIND_PARTITIONED_INDEX)
+			{
+				index_close(indexRelation, NoLock);
+				continue;
+			}
+
 			/*
 			 * If the index is valid, but cannot yet be used, ignore it; but
 			 * mark the plan we are generating as transient. See

src/test/regress/expected/cluster.out

@@ -439,6 +439,14 @@ select * from clstr_temp;
 
 drop table clstr_temp;
 RESET SESSION AUTHORIZATION;
+-- Check that partitioned tables cannot be clustered
+CREATE TABLE clstrpart (a int) PARTITION BY RANGE (a);
+CREATE INDEX clstrpart_idx ON clstrpart (a);
+ALTER TABLE clstrpart CLUSTER ON clstrpart_idx;
+ERROR:  cannot mark index clustered in partitioned table
+CLUSTER clstrpart USING clstrpart_idx;
+ERROR:  cannot cluster a partitioned table
+DROP TABLE clstrpart;
 -- Test CLUSTER with external tuplesorting
 create table clstr_4 as select * from tenk1;
 create index cluster_sort on clstr_4 (hundred, thousand, tenthous);

src/test/regress/expected/indexing.out

@@ -31,6 +31,17 @@ ERROR:  cannot create unique index on partitioned table "idxpart"
 create index concurrently on idxpart (a);
 ERROR:  cannot create index on partitioned table "idxpart" concurrently
 drop table idxpart;
+-- Verify bugfix with query on indexed partitioned table with no partitions
+-- https://postgr.es/m/20180124162006.pmapfiznhgngwtjf@alvherre.pgsql
+CREATE TABLE idxpart (col1 INT) PARTITION BY RANGE (col1);
+CREATE INDEX ON idxpart (col1);
+CREATE TABLE idxpart_two (col2 INT);
+SELECT col2 FROM idxpart_two fk LEFT OUTER JOIN idxpart pk ON (col1 = col2);
+ col2 
+------
+(0 rows)
+
+DROP table idxpart, idxpart_two;
 -- If a table without index is attached as partition to a table with
 -- an index, the index is automatically created
 create table idxpart (a int, b int, c text) partition by range (a);

src/test/regress/sql/cluster.sql

@@ -196,6 +196,13 @@ drop table clstr_temp;
 
 RESET SESSION AUTHORIZATION;
 
+-- Check that partitioned tables cannot be clustered
+CREATE TABLE clstrpart (a int) PARTITION BY RANGE (a);
+CREATE INDEX clstrpart_idx ON clstrpart (a);
+ALTER TABLE clstrpart CLUSTER ON clstrpart_idx;
+CLUSTER clstrpart USING clstrpart_idx;
+DROP TABLE clstrpart;
+
 -- Test CLUSTER with external tuplesorting
 
 create table clstr_4 as select * from tenk1;

src/test/regress/sql/indexing.sql

@@ -19,6 +19,14 @@ create unique index on idxpart (a);
 create index concurrently on idxpart (a);
 drop table idxpart;
 
+-- Verify bugfix with query on indexed partitioned table with no partitions
+-- https://postgr.es/m/20180124162006.pmapfiznhgngwtjf@alvherre.pgsql
+CREATE TABLE idxpart (col1 INT) PARTITION BY RANGE (col1);
+CREATE INDEX ON idxpart (col1);
+CREATE TABLE idxpart_two (col2 INT);
+SELECT col2 FROM idxpart_two fk LEFT OUTER JOIN idxpart pk ON (col1 = col2);
+DROP table idxpart, idxpart_two;
+
 -- If a table without index is attached as partition to a table with
 -- an index, the index is automatically created
 create table idxpart (a int, b int, c text) partition by range (a);