Preserve clustered index after rewrites with ALTER TABLE

A table rewritten by ALTER TABLE would lose tracking of an index usable
for CLUSTER.  This setting is tracked by pg_index.indisclustered and is
controlled by ALTER TABLE, so some extra work was needed to restore it
properly.  Note that ALTER TABLE only marks the index that can be used
for clustering, and does not do the actual operation.

Author: Amit Langote, Justin Pryzby
Reviewed-by: Ibrar Ahmed, Michael Paquier
Discussion: https://postgr.es/m/20200202161718[email protected]
Backpatch-through: 9.5

diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 74eb7ac8d76d18a8a30a4cdf6946fe91c673c94a..e28bdfb09dc2b3dd732cf88ef35998dd6261a269 100644 (file)
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -175,6 +175,7 @@ typedef struct AlteredTableInfo
    List       *changedIndexOids;   /* OIDs of indexes to rebuild */
    List       *changedIndexDefs;   /* string definitions of same */
    char       *replicaIdentityIndex;   /* index to reset as REPLICA IDENTITY */
+   char       *clusterOnIndex; /* index to use for CLUSTER */
 } AlteredTableInfo;
 
 /* Struct describing one new constraint to check in Phase 3 scan */
@@ -11155,6 +11156,21 @@ RememberReplicaIdentityForRebuilding(Oid indoid, AlteredTableInfo *tab)
    tab->replicaIdentityIndex = get_rel_name(indoid);
 }
 
+/*
+ * Subroutine for ATExecAlterColumnType: remember any clustered index.
+ */
+static void
+RememberClusterOnForRebuilding(Oid indoid, AlteredTableInfo *tab)
+{
+   if (!get_index_isclustered(indoid))
+       return;
+
+   if (tab->clusterOnIndex)
+       elog(ERROR, "relation %u has multiple clustered indexes", tab->relid);
+
+   tab->clusterOnIndex = get_rel_name(indoid);
+}
+
 /*
  * Subroutine for ATExecAlterColumnType: remember that a constraint needs
  * to be rebuilt (which we might already know).
@@ -11180,9 +11196,18 @@ RememberConstraintForRebuilding(Oid conoid, AlteredTableInfo *tab)
        tab->changedConstraintDefs = lappend(tab->changedConstraintDefs,
                                             defstring);
 
+       /*
+        * For the index of a constraint, if any, remember if it is used for
+        * the table's replica identity or if it is a clustered index, so that
+        * ATPostAlterTypeCleanup() can queue up commands necessary to restore
+        * those properties.
+        */
        indoid = get_constraint_index(conoid);
        if (OidIsValid(indoid))
+       {
            RememberReplicaIdentityForRebuilding(indoid, tab);
+           RememberClusterOnForRebuilding(indoid, tab);
+       }
    }
 }
 
@@ -11226,7 +11251,13 @@ RememberIndexForRebuilding(Oid indoid, AlteredTableInfo *tab)
            tab->changedIndexDefs = lappend(tab->changedIndexDefs,
                                            defstring);
 
+           /*
+            * Remember if this index is used for the table's replica identity
+            * or if it is a clustered index, so that ATPostAlterTypeCleanup()
+            * can queue up commands necessary to restore those properties.
+            */
            RememberReplicaIdentityForRebuilding(indoid, tab);
+           RememberClusterOnForRebuilding(indoid, tab);
        }
    }
 }
@@ -11353,6 +11384,21 @@ ATPostAlterTypeCleanup(List **wqueue, AlteredTableInfo *tab, LOCKMODE lockmode)
            lappend(tab->subcmds[AT_PASS_OLD_CONSTR], cmd);
    }
 
+   /*
+    * Queue up command to restore marking of index used for cluster.
+    */
+   if (tab->clusterOnIndex)
+   {
+       AlterTableCmd *cmd = makeNode(AlterTableCmd);
+
+       cmd->subtype = AT_ClusterOn;
+       cmd->name = tab->clusterOnIndex;
+
+       /* do it after indexes and constraints */
+       tab->subcmds[AT_PASS_OLD_CONSTR] =
+           lappend(tab->subcmds[AT_PASS_OLD_CONSTR], cmd);
+   }
+
    /*
     * It should be okay to use DROP_RESTRICT here, since nothing else should
     * be depending on these objects.

diff --git a/src/backend/utils/cache/lsyscache.c b/src/backend/utils/cache/lsyscache.c
index 0526b6c233aba4689cf83a94c54b6e80ac2d105e..4e9e0aad787bc2792eb55caafb91e9a62fd43260 100644 (file)
--- a/src/backend/utils/cache/lsyscache.c
+++ b/src/backend/utils/cache/lsyscache.c
@@ -3273,3 +3273,26 @@ get_index_isvalid(Oid index_oid)
 
    return isvalid;
 }
+
+/*
+ * get_index_isclustered
+ *
+ *     Given the index OID, return pg_index.indisclustered.
+ */
+bool
+get_index_isclustered(Oid index_oid)
+{
+   bool        isclustered;
+   HeapTuple   tuple;
+   Form_pg_index rd_index;
+
+   tuple = SearchSysCache1(INDEXRELID, ObjectIdGetDatum(index_oid));
+   if (!HeapTupleIsValid(tuple))
+       elog(ERROR, "cache lookup failed for index %u", index_oid);
+
+   rd_index = (Form_pg_index) GETSTRUCT(tuple);
+   isclustered = rd_index->indisclustered;
+   ReleaseSysCache(tuple);
+
+   return isclustered;
+}

diff --git a/src/include/utils/lsyscache.h b/src/include/utils/lsyscache.h
index 98bca65e45c3a33df4adeb75b9bf592167af987b..7c858be98df5b93cee85f12f91422ac40940a149 100644 (file)
--- a/src/include/utils/lsyscache.h
+++ b/src/include/utils/lsyscache.h
@@ -183,6 +183,7 @@ extern Oid  get_range_collation(Oid rangeOid);
 extern Oid get_index_column_opclass(Oid index_oid, int attno);
 extern bool    get_index_isreplident(Oid index_oid);
 extern bool get_index_isvalid(Oid index_oid);
+extern bool get_index_isclustered(Oid index_oid);
 
 #define type_is_array(typid)  (get_element_type(typid) != InvalidOid)
 /* type_is_array_domain accepts both plain arrays and domains over arrays */

diff --git a/src/test/regress/expected/alter_table.out b/src/test/regress/expected/alter_table.out
index 258530835ed6ad19397632480549329b6d027959..9e394fcbc9c5c80d7935ed6993aacd36bfb820bd 100644 (file)
--- a/src/test/regress/expected/alter_table.out
+++ b/src/test/regress/expected/alter_table.out
@@ -4186,3 +4186,51 @@ create trigger xtrig
 update bar1 set a = a + 1;
 INFO:  a=1, b=1
 /* End test case for bug #16242 */
+-- Test that ALTER TABLE rewrite preserves a clustered index
+-- for normal indexes and indexes on constraints.
+create table alttype_cluster (a int);
+alter table alttype_cluster add primary key (a);
+create index alttype_cluster_ind on alttype_cluster (a);
+alter table alttype_cluster cluster on alttype_cluster_ind;
+-- Normal index remains clustered.
+select indexrelid::regclass, indisclustered from pg_index
+  where indrelid = 'alttype_cluster'::regclass
+  order by indexrelid::regclass::text;
+      indexrelid      | indisclustered 
+----------------------+----------------
+ alttype_cluster_ind  | t
+ alttype_cluster_pkey | f
+(2 rows)
+
+alter table alttype_cluster alter a type bigint;
+select indexrelid::regclass, indisclustered from pg_index
+  where indrelid = 'alttype_cluster'::regclass
+  order by indexrelid::regclass::text;
+      indexrelid      | indisclustered 
+----------------------+----------------
+ alttype_cluster_ind  | t
+ alttype_cluster_pkey | f
+(2 rows)
+
+-- Constraint index remains clustered.
+alter table alttype_cluster cluster on alttype_cluster_pkey;
+select indexrelid::regclass, indisclustered from pg_index
+  where indrelid = 'alttype_cluster'::regclass
+  order by indexrelid::regclass::text;
+      indexrelid      | indisclustered 
+----------------------+----------------
+ alttype_cluster_ind  | f
+ alttype_cluster_pkey | t
+(2 rows)
+
+alter table alttype_cluster alter a type int;
+select indexrelid::regclass, indisclustered from pg_index
+  where indrelid = 'alttype_cluster'::regclass
+  order by indexrelid::regclass::text;
+      indexrelid      | indisclustered 
+----------------------+----------------
+ alttype_cluster_ind  | f
+ alttype_cluster_pkey | t
+(2 rows)
+
+drop table alttype_cluster;

diff --git a/src/test/regress/sql/alter_table.sql b/src/test/regress/sql/alter_table.sql
index 0e8f7015c9d4041303a3e9f5e79179ae57131fba..67646da2797c5f15be7ad53f93a39c0136fa404c 100644 (file)
--- a/src/test/regress/sql/alter_table.sql
+++ b/src/test/regress/sql/alter_table.sql
@@ -2814,3 +2814,28 @@ create trigger xtrig
 update bar1 set a = a + 1;
 
 /* End test case for bug #16242 */
+
+-- Test that ALTER TABLE rewrite preserves a clustered index
+-- for normal indexes and indexes on constraints.
+create table alttype_cluster (a int);
+alter table alttype_cluster add primary key (a);
+create index alttype_cluster_ind on alttype_cluster (a);
+alter table alttype_cluster cluster on alttype_cluster_ind;
+-- Normal index remains clustered.
+select indexrelid::regclass, indisclustered from pg_index
+  where indrelid = 'alttype_cluster'::regclass
+  order by indexrelid::regclass::text;
+alter table alttype_cluster alter a type bigint;
+select indexrelid::regclass, indisclustered from pg_index
+  where indrelid = 'alttype_cluster'::regclass
+  order by indexrelid::regclass::text;
+-- Constraint index remains clustered.
+alter table alttype_cluster cluster on alttype_cluster_pkey;
+select indexrelid::regclass, indisclustered from pg_index
+  where indrelid = 'alttype_cluster'::regclass
+  order by indexrelid::regclass::text;
+alter table alttype_cluster alter a type int;
+select indexrelid::regclass, indisclustered from pg_index
+  where indrelid = 'alttype_cluster'::regclass
+  order by indexrelid::regclass::text;
+drop table alttype_cluster;