On Tue, Jul 20, 2021 at 08:27:02PM -0400, Alvaro Herrera wrote:
> I have to wonder if there really *is* a use case for CLUSTER in the
> first place on regular tables, let alone on partitioned tables, which
> are likely to be large and thus take a lot of time.
The cluster now is done one partition at a time, so it might take a long time,
but doesn't lock the whole partition heirarchy. Same as VACUUM (since v10) and
(since v14) REINDEX.
The patch series would be simpler if partitioned indexes weren't allowed to be
marked CLUSTERED ON. Then, "USING <index>" would be required, which is a step
forward from not supporting cluster on partitioned index at all. As attached.
It's arguably true that the follow-up patches supporting indisclustered on
partitioned indexes aren't worth the trouble.
For sure CLUSTER is useful, see eg.
https://github.com/bucardo/check_postgres/issues/29
It's sometimes important that the table is clustered to allow index scan to
work well (or be chosen at all).
If a table is scanned by an index, and isn't well-clustered, then a larger
fraction (multiple) of the table will be read than what's optimal. That
requires more IO, and more cache space.
A year ago, I partitioned one of our previously-unpartitioned tables, and ended
up clustering the partitions on their partition key (and indexed column) using
\gexec. This was preferable to doing INSERT .. SELECT .. ORDER BY, which
would've made the initial process slower - maybe unjustifiably slower for some
customers. Cluster (using \gexec) was something I was able to do afterward,
for completeness, since I expect the partitions to be mostly-clustered
automatically, so it was bothering me that the existing data was unordered, and
that it might behave differently in the future.
> What justifies spending so much time on this implementation?
Actually, I don't use partitioned indexes at all here, so this is not for us..
I worked on this after Adger asked about CIC on partitioned tables (for which I
have a patch in the queue). Isn't it worth supporting that (or should we
include an example about how to use format() with %I and \gexec) ?
VACUUM [FULL] has recursed into partitions since v10 (f0e44751d).
REINDEX supports partitioned tables in v14 (a6642b3ae).
Partitioned indexes exist since v11 (as you well know), so it's somewhat odd
that CLUSTER isn't supported, and seems increasingly weird as decreasing number
of DDL commands are not supported. Supporting DDL on partitioned tables
supports the idea that the physical partitions can be seen as an implementation
detail by the DBA, which I understand was the intent since v10.
You're right that I wouldn't plan to *routinely* re-cluster a partitioned
table. Rather, I'd cluster only its "recent" *partitions*, and leave the old
ones alone. Or cluster the partitions, a single time, once they're no longer
recent. I don't think the feature is marginal just because I don't use it
routinely.
> My impression is that CLUSTER is pretty much a fringe command nowadays,
> because of the access exclusive lock required.
A step forward would be to integrate something like pg_repack/reorg/squeeze.
I used pg_repack --index until v12 got REINDEX CONCURRENTLY. The goal there
was to improve index scans on some large, append-only partitions where the
planner gave an index scan, but performance was poor (now, we use BRIN so it
works well without reindex). I tested that this would still be an issue by
creating a non-brin index for a single day's table (even with v13 deduplication
and v12 TID tiebreak).
As I see it, support for partitioned cluster is orthogonal to an
online/concurrent cluster, which is a job for another patch.
--
Justin
>From d2e7daf9c05cd3c20c60f5e35c0d6b2612d75d1b Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryz...@telsasoft.com>
Date: Sun, 7 Jun 2020 16:58:42 -0500
Subject: [PATCH v11] Implement CLUSTER of partitioned table..
For now, partitioned indexes cannot be marked clustered, so clustering requires
specification of a partitioned index on the partitioned table.
VACUUM (including vacuum full) has recursed into partitione tables since
partitioning were introduced in v10 (3c3bb9933). See expand_vacuum_rel().
See also a556549d7 and 19de0ab23.
---
doc/src/sgml/ref/cluster.sgml | 6 +
src/backend/commands/cluster.c | 170 +++++++++++++++++++-------
src/bin/psql/tab-complete.c | 1 +
src/include/commands/cluster.h | 1 +
src/test/regress/expected/cluster.out | 46 ++++++-
src/test/regress/sql/cluster.sql | 22 +++-
6 files changed, 197 insertions(+), 49 deletions(-)
diff --git a/doc/src/sgml/ref/cluster.sgml b/doc/src/sgml/ref/cluster.sgml
index 86f5fdc469..b3463ae5c4 100644
--- a/doc/src/sgml/ref/cluster.sgml
+++ b/doc/src/sgml/ref/cluster.sgml
@@ -196,6 +196,12 @@ CLUSTER [VERBOSE]
in the <structname>pg_stat_progress_cluster</structname> view. See
<xref linkend="cluster-progress-reporting"/> for details.
</para>
+
+ <para>
+ Clustering a partitioned table clusters each of its partitions using the
+ partition of the specified partitioned index (which must be specified).
+ </para>
+
</refsect1>
<refsect1>
diff --git a/src/backend/commands/cluster.c b/src/backend/commands/cluster.c
index 9d22f648a8..c5923c5217 100644
--- a/src/backend/commands/cluster.c
+++ b/src/backend/commands/cluster.c
@@ -32,7 +32,9 @@
#include "catalog/index.h"
#include "catalog/namespace.h"
#include "catalog/objectaccess.h"
+#include "catalog/partition.h"
#include "catalog/pg_am.h"
+#include "catalog/pg_inherits.h"
#include "catalog/toasting.h"
#include "commands/cluster.h"
#include "commands/defrem.h"
@@ -73,6 +75,9 @@ static void copy_table_data(Oid OIDNewHeap, Oid OIDOldHeap, Oid OIDOldIndex,
bool verbose, bool *pSwapToastByContent,
TransactionId *pFreezeXid, MultiXactId *pCutoffMulti);
static List *get_tables_to_cluster(MemoryContext cluster_context);
+static List *get_tables_to_cluster_partitioned(MemoryContext cluster_context,
+ Oid indexOid);
+static void cluster_multiple_rels(List *rvs, int options);
/*---------------------------------------------------------------------------
@@ -131,6 +136,7 @@ cluster(ParseState *pstate, ClusterStmt *stmt, bool isTopLevel)
Relation rel;
/* Find, lock, and check permissions on the table */
+ /* Obtain AEL now to avoid lock-upgrade hazard in the single-transaction case */
tableOid = RangeVarGetRelidExtended(stmt->relation,
AccessExclusiveLock,
0,
@@ -146,14 +152,6 @@ cluster(ParseState *pstate, 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;
@@ -188,11 +186,45 @@ cluster(ParseState *pstate, ClusterStmt *stmt, bool isTopLevel)
stmt->indexname, stmt->relation->relname)));
}
- /* close relation, keep lock till commit */
- table_close(rel, NoLock);
+ if (rel->rd_rel->relkind != RELKIND_PARTITIONED_TABLE)
+ {
+ /* close relation, keep lock till commit */
+ table_close(rel, NoLock);
- /* Do the job. */
- cluster_rel(tableOid, indexOid, ¶ms);
+ /* Do the job. */
+ cluster_rel(tableOid, indexOid, ¶ms);
+ }
+ else
+ {
+ List *rvs;
+ MemoryContext cluster_context;
+
+ /* Refuse to hold strong locks in a user transaction */
+ PreventInTransactionBlock(isTopLevel, "CLUSTER");
+
+ cluster_context = AllocSetContextCreate(PortalContext,
+ "Cluster",
+ ALLOCSET_DEFAULT_SIZES);
+
+ rvs = get_tables_to_cluster_partitioned(cluster_context, indexOid);
+
+ /*
+ * For now, partitioned indexes are not actually marked clustered.
+ */
+ check_index_is_clusterable(rel, indexOid, true, AccessShareLock);
+
+ /* close relation, releasing lock on parent table */
+ table_close(rel, AccessExclusiveLock);
+
+ /* Do the job. */
+ cluster_multiple_rels(rvs, params.options);
+
+ /* Start a new transaction for the cleanup work. */
+ StartTransactionCommand();
+
+ /* Clean up working storage */
+ MemoryContextDelete(cluster_context);
+ }
}
else
{
@@ -202,7 +234,6 @@ cluster(ParseState *pstate, ClusterStmt *stmt, bool isTopLevel)
*/
MemoryContext cluster_context;
List *rvs;
- ListCell *rv;
/*
* We cannot run this form of CLUSTER inside a user transaction block;
@@ -225,28 +256,7 @@ cluster(ParseState *pstate, ClusterStmt *stmt, bool isTopLevel)
* cluster_context.
*/
rvs = get_tables_to_cluster(cluster_context);
-
- /* Commit to get out of starting transaction */
- PopActiveSnapshot();
- CommitTransactionCommand();
-
- /* Ok, now that we've got them all, cluster them one by one */
- foreach(rv, rvs)
- {
- RelToCluster *rvtc = (RelToCluster *) lfirst(rv);
- ClusterParams cluster_params = params;
-
- /* Start a new transaction for each relation. */
- StartTransactionCommand();
- /* functions in indexes may want a snapshot set */
- PushActiveSnapshot(GetTransactionSnapshot());
- /* Do the job. */
- cluster_params.options |= CLUOPT_RECHECK;
- cluster_rel(rvtc->tableOid, rvtc->indexOid,
- &cluster_params);
- PopActiveSnapshot();
- CommitTransactionCommand();
- }
+ cluster_multiple_rels(rvs, params.options | CLUOPT_RECHECK_ISCLUSTERED);
/* Start a new transaction for the cleanup work. */
StartTransactionCommand();
@@ -327,10 +337,11 @@ cluster_rel(Oid tableOid, Oid indexOid, ClusterParams *params)
/*
* Silently skip a temp table for a remote session. Only doing this
* check in the "recheck" case is appropriate (which currently means
- * somebody is executing a database-wide CLUSTER), because there is
- * another check in cluster() which will stop any attempt to cluster
- * remote temp tables by name. There is another check in cluster_rel
- * which is redundant, but we leave it for extra safety.
+ * somebody is executing a database-wide CLUSTER or on a partitioned
+ * table), because there is another check in cluster() which will stop
+ * any attempt to cluster remote temp tables by name. There is another
+ * check in cluster_rel which is redundant, but we leave it for extra
+ * safety.
*/
if (RELATION_IS_OTHER_TEMP(OldHeap))
{
@@ -352,9 +363,10 @@ cluster_rel(Oid tableOid, Oid indexOid, ClusterParams *params)
}
/*
- * Check that the index is still the one with indisclustered set.
+ * Check that the index is still the one with indisclustered set, if needed.
*/
- if (!get_index_isclustered(indexOid))
+ if ((params->options & CLUOPT_RECHECK_ISCLUSTERED) != 0 &&
+ !get_index_isclustered(indexOid))
{
relation_close(OldHeap, AccessExclusiveLock);
pgstat_progress_end_command();
@@ -415,6 +427,9 @@ cluster_rel(Oid tableOid, Oid indexOid, ClusterParams *params)
return;
}
+ // Should silently skip this rather than assert ?
+ Assert(RELKIND_HAS_STORAGE(OldHeap->rd_rel->relkind));
+
/*
* All predicate locks on the tuples or pages are about to be made
* invalid, because we move tuples around. Promote them to relation
@@ -585,8 +600,8 @@ rebuild_relation(Relation OldHeap, Oid indexOid, bool verbose)
TransactionId frozenXid;
MultiXactId cutoffMulti;
- /* Mark the correct index as clustered */
if (OidIsValid(indexOid))
+ /* Mark the correct index as clustered */
mark_index_clustered(OldHeap, indexOid, true);
/* Remember info about rel before closing OldHeap */
@@ -1604,3 +1619,74 @@ get_tables_to_cluster(MemoryContext cluster_context)
return rvs;
}
+
+/*
+ * Return a List of tables and their associated indexes, where each index is a
+ * partition of the given index
+ */
+static List *
+get_tables_to_cluster_partitioned(MemoryContext cluster_context, Oid indexOid)
+{
+ List *inhoids;
+ ListCell *lc;
+ List *rvs = NIL;
+ MemoryContext old_context;
+
+ inhoids = find_all_inheritors(indexOid, NoLock, NULL);
+
+ /*
+ * We have to build the list in a different memory context so it will
+ * survive the cross-transaction processing
+ */
+ old_context = MemoryContextSwitchTo(cluster_context);
+
+ foreach(lc, inhoids)
+ {
+ Oid indexrelid = lfirst_oid(lc);
+ Oid relid = IndexGetRelation(indexrelid, false);
+ RelToCluster *rvtc;
+
+ if (!RELKIND_HAS_STORAGE(get_rel_relkind(indexrelid)))
+ continue;
+
+ rvtc = (RelToCluster *) palloc(sizeof(RelToCluster));
+ rvtc->tableOid = relid;
+ rvtc->indexOid = indexrelid;
+ rvs = lappend(rvs, rvtc);
+ }
+
+ MemoryContextSwitchTo(old_context);
+ return rvs;
+}
+
+/* Cluster each relation in a separate transaction */
+static void
+cluster_multiple_rels(List *rvs, int options)
+{
+ ListCell *lc;
+
+ /* Commit to get out of starting transaction */
+ PopActiveSnapshot();
+ CommitTransactionCommand();
+
+ /* Ok, now that we've got them all, cluster them one by one */
+ foreach(lc, rvs)
+ {
+ RelToCluster *rvtc = (RelToCluster *) lfirst(lc);
+ ClusterParams cluster_params = { .options = options, };
+
+ /* Start a new transaction for each relation. */
+ StartTransactionCommand();
+
+ /* functions in indexes may want a snapshot set */
+ PushActiveSnapshot(GetTransactionSnapshot());
+
+ /* Do the job. */
+ cluster_params.options |= CLUOPT_RECHECK;
+ cluster_rel(rvtc->tableOid, rvtc->indexOid,
+ &cluster_params);
+
+ PopActiveSnapshot();
+ CommitTransactionCommand();
+ }
+}
diff --git a/src/bin/psql/tab-complete.c b/src/bin/psql/tab-complete.c
index 5cd5838668..c377511278 100644
--- a/src/bin/psql/tab-complete.c
+++ b/src/bin/psql/tab-complete.c
@@ -599,6 +599,7 @@ static const SchemaQuery Query_for_list_of_clusterables = {
.catname = "pg_catalog.pg_class c",
.selcondition =
"c.relkind IN (" CppAsString2(RELKIND_RELATION) ", "
+ CppAsString2(RELKIND_PARTITIONED_TABLE) ", "
CppAsString2(RELKIND_MATVIEW) ")",
.viscondition = "pg_catalog.pg_table_is_visible(c.oid)",
.namespace = "c.relnamespace",
diff --git a/src/include/commands/cluster.h b/src/include/commands/cluster.h
index b64d3bc204..d400b6e937 100644
--- a/src/include/commands/cluster.h
+++ b/src/include/commands/cluster.h
@@ -22,6 +22,7 @@
/* flag bits for ClusterParams->flags */
#define CLUOPT_RECHECK 0x01 /* recheck relation state */
#define CLUOPT_VERBOSE 0x02 /* print progress info */
+#define CLUOPT_RECHECK_ISCLUSTERED 0x04 /* recheck relation state for indisclustered */
/* options for CLUSTER */
typedef struct ClusterParams
diff --git a/src/test/regress/expected/cluster.out b/src/test/regress/expected/cluster.out
index e46a66952f..7461e1c090 100644
--- a/src/test/regress/expected/cluster.out
+++ b/src/test/regress/expected/cluster.out
@@ -444,14 +444,52 @@ 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(10);
+CREATE TABLE clstrpart12 PARTITION OF clstrpart1 FOR VALUES FROM (10)TO(20) PARTITION BY RANGE(a);
+CREATE TABLE clstrpart2 PARTITION OF clstrpart FOR VALUES FROM (20)TO(30);
+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;
create index cluster_sort on clstr_4 (hundred, thousand, tenthous);
diff --git a/src/test/regress/sql/cluster.sql b/src/test/regress/sql/cluster.sql
index aee9cf83e0..f31f8ef2b2 100644
--- a/src/test/regress/sql/cluster.sql
+++ b/src/test/regress/sql/cluster.sql
@@ -202,12 +202,28 @@ 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(10);
+CREATE TABLE clstrpart12 PARTITION OF clstrpart1 FOR VALUES FROM (10)TO(20) PARTITION BY RANGE(a);
+CREATE TABLE clstrpart2 PARTITION OF clstrpart FOR VALUES FROM (20)TO(30);
+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;
-DROP TABLE clstrpart;
+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;
-- Test CLUSTER with external tuplesorting
--
2.17.0
