Allow CLUSTER on partitioned tables

This is essentially the same as applying VACUUM FULL to a partitioned
table, which has been supported since commit 3c3bb99330aa (March 2017).
While there's no great use case in applying CLUSTER to partitioned
tables, we don't have any strong reason not to allow it either.

For now, partitioned indexes cannot be marked clustered, so an index
must always be specified.

While at it, rename some variables that were RangeVars during the
development that led to 8bc717cb8878 but never made it that way to the
source tree; there's no need to perpetuate names that have always been
more confusing than helpful.

Author: Justin Pryzby <pryzby@telsasoft.com>
Reviewed-by: Matthias van de Meent <boekewurm+postgres@gmail.com>
Discussion: https://postgr.es/m/20201028003312.GU9241@telsasoft.com
Discussion: https://postgr.es/m/20200611153502.GT14879@telsasoft.com

2 files changed, 66 insertions, 5 deletions

diff --git a/src/test/regress/expected/cluster.out b/src/test/regress/expected/cluster.out
index e46a66952f0..953818c74e1 100644
--- a/src/test/regress/expected/cluster.out
+++ b/src/test/regress/expected/cluster.out
@@ -305,6 +305,8 @@ WHERE pg_class.oid=indexrelid
 ---------
 (0 rows)
 
+-- Verify that toast tables are clusterable
+CLUSTER pg_toast.pg_toast_826 USING pg_toast_826_index;
 -- Verify that clustering all tables does in fact cluster the right ones
 CREATE USER regress_clstr_user;
 CREATE TABLE clstr_1 (a INT PRIMARY KEY);
@@ -444,13 +446,52 @@ DROP TABLE clustertest;
 CREATE TABLE clustertest (f1 int PRIMARY KEY);
 CLUSTER clustertest USING clustertest_pkey;
 CLUSTER clustertest;
--- Check that partitioned tables cannot be clustered
+-- Check that partitioned tables can be clustered
 CREATE TABLE clstrpart (a int) PARTITION BY RANGE (a);
+CREATE TABLE clstrpart1 PARTITION OF clstrpart FOR VALUES FROM (1) TO (10) PARTITION BY RANGE (a);
+CREATE TABLE clstrpart11 PARTITION OF clstrpart1 FOR VALUES FROM (1) TO (5);
+CREATE TABLE clstrpart12 PARTITION OF clstrpart1 FOR VALUES FROM (5) TO (10) PARTITION BY RANGE (a);
+CREATE TABLE clstrpart2 PARTITION OF clstrpart FOR VALUES FROM (10) TO (20);
+CREATE TABLE clstrpart3 PARTITION OF clstrpart DEFAULT PARTITION BY RANGE (a);
+CREATE TABLE clstrpart33 PARTITION OF clstrpart3 DEFAULT;
+CREATE INDEX clstrpart_only_idx ON ONLY clstrpart (a);
+CLUSTER clstrpart USING clstrpart_only_idx; -- fails
+ERROR:  cannot cluster on invalid index "clstrpart_only_idx"
+DROP INDEX clstrpart_only_idx;
 CREATE INDEX clstrpart_idx ON clstrpart (a);
+-- Check that clustering sets new relfilenodes:
+CREATE TEMP TABLE old_cluster_info AS SELECT relname, level, relfilenode, relkind FROM pg_partition_tree('clstrpart'::regclass) AS tree JOIN pg_class c ON c.oid=tree.relid ;
+CLUSTER clstrpart USING clstrpart_idx;
+CREATE TEMP TABLE new_cluster_info AS SELECT relname, level, relfilenode, relkind FROM pg_partition_tree('clstrpart'::regclass) AS tree JOIN pg_class c ON c.oid=tree.relid ;
+SELECT relname, old.level, old.relkind, old.relfilenode = new.relfilenode FROM old_cluster_info AS old JOIN new_cluster_info AS new USING (relname) ORDER BY relname COLLATE "C";
+   relname   | level | relkind | ?column? 
+-------------+-------+---------+----------
+ clstrpart   |     0 | p       | t
+ clstrpart1  |     1 | p       | t
+ clstrpart11 |     2 | r       | f
+ clstrpart12 |     2 | p       | t
+ clstrpart2  |     1 | r       | f
+ clstrpart3  |     1 | p       | t
+ clstrpart33 |     2 | r       | f
+(7 rows)
+
+-- Partitioned indexes aren't and can't be marked un/clustered:
+\d clstrpart
+       Partitioned table "public.clstrpart"
+ Column |  Type   | Collation | Nullable | Default 
+--------+---------+-----------+----------+---------
+ a      | integer |           |          | 
+Partition key: RANGE (a)
+Indexes:
+    "clstrpart_idx" btree (a)
+Number of partitions: 3 (Use \d+ to list them.)
+
+CLUSTER clstrpart;
+ERROR:  there is no previously clustered index for table "clstrpart"
+ALTER TABLE clstrpart SET WITHOUT CLUSTER;
+ERROR:  cannot mark index clustered in partitioned table
 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;
diff --git a/src/test/regress/sql/cluster.sql b/src/test/regress/sql/cluster.sql
index aee9cf83e04..5601684ee3f 100644
--- a/src/test/regress/sql/cluster.sql
+++ b/src/test/regress/sql/cluster.sql
@@ -104,6 +104,9 @@ WHERE pg_class.oid=indexrelid
 	AND pg_class_2.relname = 'clstr_tst'
 	AND indisclustered;
 
+-- Verify that toast tables are clusterable
+CLUSTER pg_toast.pg_toast_826 USING pg_toast_826_index;
+
 -- Verify that clustering all tables does in fact cluster the right ones
 CREATE USER regress_clstr_user;
 CREATE TABLE clstr_1 (a INT PRIMARY KEY);
@@ -202,11 +205,28 @@ CREATE TABLE clustertest (f1 int PRIMARY KEY);
 CLUSTER clustertest USING clustertest_pkey;
 CLUSTER clustertest;
 
--- Check that partitioned tables cannot be clustered
+-- Check that partitioned tables can be clustered
 CREATE TABLE clstrpart (a int) PARTITION BY RANGE (a);
+CREATE TABLE clstrpart1 PARTITION OF clstrpart FOR VALUES FROM (1) TO (10) PARTITION BY RANGE (a);
+CREATE TABLE clstrpart11 PARTITION OF clstrpart1 FOR VALUES FROM (1) TO (5);
+CREATE TABLE clstrpart12 PARTITION OF clstrpart1 FOR VALUES FROM (5) TO (10) PARTITION BY RANGE (a);
+CREATE TABLE clstrpart2 PARTITION OF clstrpart FOR VALUES FROM (10) TO (20);
+CREATE TABLE clstrpart3 PARTITION OF clstrpart DEFAULT PARTITION BY RANGE (a);
+CREATE TABLE clstrpart33 PARTITION OF clstrpart3 DEFAULT;
+CREATE INDEX clstrpart_only_idx ON ONLY clstrpart (a);
+CLUSTER clstrpart USING clstrpart_only_idx; -- fails
+DROP INDEX clstrpart_only_idx;
 CREATE INDEX clstrpart_idx ON clstrpart (a);
-ALTER TABLE clstrpart CLUSTER ON clstrpart_idx;
+-- Check that clustering sets new relfilenodes:
+CREATE TEMP TABLE old_cluster_info AS SELECT relname, level, relfilenode, relkind FROM pg_partition_tree('clstrpart'::regclass) AS tree JOIN pg_class c ON c.oid=tree.relid ;
 CLUSTER clstrpart USING clstrpart_idx;
+CREATE TEMP TABLE new_cluster_info AS SELECT relname, level, relfilenode, relkind FROM pg_partition_tree('clstrpart'::regclass) AS tree JOIN pg_class c ON c.oid=tree.relid ;
+SELECT relname, old.level, old.relkind, old.relfilenode = new.relfilenode FROM old_cluster_info AS old JOIN new_cluster_info AS new USING (relname) ORDER BY relname COLLATE "C";
+-- Partitioned indexes aren't and can't be marked un/clustered:
+\d clstrpart
+CLUSTER clstrpart;
+ALTER TABLE clstrpart SET WITHOUT CLUSTER;
+ALTER TABLE clstrpart CLUSTER ON clstrpart_idx;
 DROP TABLE clstrpart;
 
 -- Test CLUSTER with external tuplesorting