pgstat: Fix transactional stats dropping for indexes

Because index creation does not go through heap_create_with_catalog() we
didn't call pgstat_create_relation(), leading to index stats of a newly
created realtion not getting dropped during rollback. To fix, move the
pgstat_create_relation() to heap_create(), which indexes do use.

Similarly, because dropping an index does not go through
heap_drop_with_catalog(), we didn't drop index stats when the transaction
dropping an index committed. Here there's no convenient common path for
indexes and relations, so index_drop() now calls pgstat_drop_relation().

Add tests for transactional index stats handling.

Author: "Drouvot, Bertrand" <bdrouvot@amazon.com>
Reviewed-by: Andres Freund <andres@anarazel.de>
Reviewed-by: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Discussion: https://postgr.es/m/51bbf286-2b4a-8998-bd12-eaae4b765d99@amazon.com
Backpatch: 15-, like 8b1dccd37c, which introduced the bug

src/backend/catalog/heap.c

@@ -403,6 +403,9 @@ heap_create(const char *relname,
 		recordDependencyOnTablespace(RelationRelationId, relid,
 									 reltablespace);
 
+	/* ensure that stats are dropped if transaction aborts */
+	pgstat_create_relation(rel);
+
 	return rel;
 }
 
@@ -1477,9 +1480,6 @@ heap_create_with_catalog(const char *relname,
 	if (oncommit != ONCOMMIT_NOOP)
 		register_on_commit_action(relid, oncommit);
 
-	/* ensure that stats are dropped if transaction aborts */
-	pgstat_create_relation(new_rel_desc);
-
 	/*
 	 * ok, the relation has been cataloged, so close our relations and return
 	 * the OID of the newly created relation.

src/backend/catalog/index.c

@@ -2325,6 +2325,9 @@ index_drop(Oid indexId, bool concurrent, bool concurrent_lock_mode)
 	if (RELKIND_HAS_STORAGE(userIndexRelation->rd_rel->relkind))
 		RelationDropStorage(userIndexRelation);
 
+	/* ensure that stats are dropped if transaction commits */
+	pgstat_drop_relation(userIndexRelation);
+
 	/*
 	 * Close and flush the index's relcache entry, to ensure relcache doesn't
 	 * try to rebuild it while we're deleting catalog entries. We keep the

src/test/regress/expected/stats.out

@@ -18,6 +18,8 @@ SET enable_indexscan TO on;
 SET enable_indexonlyscan TO off;
 -- not enabled by default, but we want to test it...
 SET track_functions TO 'all';
+-- record dboid for later use
+SELECT oid AS dboid from pg_database where datname = current_database() \gset
 -- save counters
 BEGIN;
 SET LOCAL stats_fetch_consistency = snapshot;
@@ -777,18 +779,121 @@ SELECT pg_stat_have_stats('bgwriter', 0, 0);
 SELECT pg_stat_have_stats('zaphod', 0, 0);
 ERROR:  invalid statistics kind: "zaphod"
 -- db stats have objoid 0
-SELECT pg_stat_have_stats('database', (SELECT oid FROM pg_database WHERE datname = current_database()), 1);
+SELECT pg_stat_have_stats('database', :dboid, 1);
  pg_stat_have_stats 
 --------------------
  f
 (1 row)
 
-SELECT pg_stat_have_stats('database', (SELECT oid FROM pg_database WHERE datname = current_database()), 0);
+SELECT pg_stat_have_stats('database', :dboid, 0);
  pg_stat_have_stats 
 --------------------
  t
 (1 row)
 
+-- pg_stat_have_stats returns true for committed index creation
+CREATE table stats_test_tab1 as select generate_series(1,10) a;
+CREATE index stats_test_idx1 on stats_test_tab1(a);
+SELECT 'stats_test_idx1'::regclass::oid AS stats_test_idx1_oid \gset
+SET enable_seqscan TO off;
+select a from stats_test_tab1 where a = 3;
+ a 
+---
+ 3
+(1 row)
+
+SELECT pg_stat_have_stats('relation', :dboid, :stats_test_idx1_oid);
+ pg_stat_have_stats 
+--------------------
+ t
+(1 row)
+
+-- pg_stat_have_stats returns false for dropped index with stats
+SELECT pg_stat_have_stats('relation', :dboid, :stats_test_idx1_oid);
+ pg_stat_have_stats 
+--------------------
+ t
+(1 row)
+
+DROP index stats_test_idx1;
+SELECT pg_stat_have_stats('relation', :dboid, :stats_test_idx1_oid);
+ pg_stat_have_stats 
+--------------------
+ f
+(1 row)
+
+-- pg_stat_have_stats returns false for rolled back index creation
+BEGIN;
+CREATE index stats_test_idx1 on stats_test_tab1(a);
+SELECT 'stats_test_idx1'::regclass::oid AS stats_test_idx1_oid \gset
+select a from stats_test_tab1 where a = 3;
+ a 
+---
+ 3
+(1 row)
+
+SELECT pg_stat_have_stats('relation', :dboid, :stats_test_idx1_oid);
+ pg_stat_have_stats 
+--------------------
+ t
+(1 row)
+
+ROLLBACK;
+SELECT pg_stat_have_stats('relation', :dboid, :stats_test_idx1_oid);
+ pg_stat_have_stats 
+--------------------
+ f
+(1 row)
+
+-- pg_stat_have_stats returns true for reindex CONCURRENTLY
+CREATE index stats_test_idx1 on stats_test_tab1(a);
+SELECT 'stats_test_idx1'::regclass::oid AS stats_test_idx1_oid \gset
+select a from stats_test_tab1 where a = 3;
+ a 
+---
+ 3
+(1 row)
+
+SELECT pg_stat_have_stats('relation', :dboid, :stats_test_idx1_oid);
+ pg_stat_have_stats 
+--------------------
+ t
+(1 row)
+
+REINDEX index CONCURRENTLY stats_test_idx1;
+-- false for previous oid
+SELECT pg_stat_have_stats('relation', :dboid, :stats_test_idx1_oid);
+ pg_stat_have_stats 
+--------------------
+ f
+(1 row)
+
+-- true for new oid
+SELECT 'stats_test_idx1'::regclass::oid AS stats_test_idx1_oid \gset
+SELECT pg_stat_have_stats('relation', :dboid, :stats_test_idx1_oid);
+ pg_stat_have_stats 
+--------------------
+ t
+(1 row)
+
+-- pg_stat_have_stats returns true for a rolled back drop index with stats
+BEGIN;
+SELECT pg_stat_have_stats('relation', :dboid, :stats_test_idx1_oid);
+ pg_stat_have_stats 
+--------------------
+ t
+(1 row)
+
+DROP index stats_test_idx1;
+ROLLBACK;
+SELECT pg_stat_have_stats('relation', :dboid, :stats_test_idx1_oid);
+ pg_stat_have_stats 
+--------------------
+ t
+(1 row)
+
+-- put enable_seqscan back to on
+SET enable_seqscan TO on;
 -- ensure that stats accessors handle NULL input correctly
 SELECT pg_stat_get_replication_slot(NULL);
  pg_stat_get_replication_slot 

src/test/regress/sql/stats.sql

@@ -16,6 +16,9 @@ SET enable_indexonlyscan TO off;
 -- not enabled by default, but we want to test it...
 SET track_functions TO 'all';
 
+-- record dboid for later use
+SELECT oid AS dboid from pg_database where datname = current_database() \gset
+
 -- save counters
 BEGIN;
 SET LOCAL stats_fetch_consistency = snapshot;
@@ -388,9 +391,52 @@ SELECT pg_stat_have_stats('bgwriter', 0, 0);
 -- unknown stats kinds error out
 SELECT pg_stat_have_stats('zaphod', 0, 0);
 -- db stats have objoid 0
-SELECT pg_stat_have_stats('database', (SELECT oid FROM pg_database WHERE datname = current_database()), 1);
+SELECT pg_stat_have_stats('database', :dboid, 1);
-SELECT pg_stat_have_stats('database', (SELECT oid FROM pg_database WHERE datname = current_database()), 0);
+SELECT pg_stat_have_stats('database', :dboid, 0);
 
+-- pg_stat_have_stats returns true for committed index creation
+CREATE table stats_test_tab1 as select generate_series(1,10) a;
+CREATE index stats_test_idx1 on stats_test_tab1(a);
+SELECT 'stats_test_idx1'::regclass::oid AS stats_test_idx1_oid \gset
+SET enable_seqscan TO off;
+select a from stats_test_tab1 where a = 3;
+SELECT pg_stat_have_stats('relation', :dboid, :stats_test_idx1_oid);
+
+-- pg_stat_have_stats returns false for dropped index with stats
+SELECT pg_stat_have_stats('relation', :dboid, :stats_test_idx1_oid);
+DROP index stats_test_idx1;
+SELECT pg_stat_have_stats('relation', :dboid, :stats_test_idx1_oid);
+
+-- pg_stat_have_stats returns false for rolled back index creation
+BEGIN;
+CREATE index stats_test_idx1 on stats_test_tab1(a);
+SELECT 'stats_test_idx1'::regclass::oid AS stats_test_idx1_oid \gset
+select a from stats_test_tab1 where a = 3;
+SELECT pg_stat_have_stats('relation', :dboid, :stats_test_idx1_oid);
+ROLLBACK;
+SELECT pg_stat_have_stats('relation', :dboid, :stats_test_idx1_oid);
+
+-- pg_stat_have_stats returns true for reindex CONCURRENTLY
+CREATE index stats_test_idx1 on stats_test_tab1(a);
+SELECT 'stats_test_idx1'::regclass::oid AS stats_test_idx1_oid \gset
+select a from stats_test_tab1 where a = 3;
+SELECT pg_stat_have_stats('relation', :dboid, :stats_test_idx1_oid);
+REINDEX index CONCURRENTLY stats_test_idx1;
+-- false for previous oid
+SELECT pg_stat_have_stats('relation', :dboid, :stats_test_idx1_oid);
+-- true for new oid
+SELECT 'stats_test_idx1'::regclass::oid AS stats_test_idx1_oid \gset
+SELECT pg_stat_have_stats('relation', :dboid, :stats_test_idx1_oid);
+
+-- pg_stat_have_stats returns true for a rolled back drop index with stats
+BEGIN;
+SELECT pg_stat_have_stats('relation', :dboid, :stats_test_idx1_oid);
+DROP index stats_test_idx1;
+ROLLBACK;
+SELECT pg_stat_have_stats('relation', :dboid, :stats_test_idx1_oid);
+
+-- put enable_seqscan back to on
+SET enable_seqscan TO on;
 
 -- ensure that stats accessors handle NULL input correctly
 SELECT pg_stat_get_replication_slot(NULL);