Reintroduce support for sequences in pgstattuple and pageinspect.

Commit 4b82664156 restricted a number of functions provided by
contrib modules to only relations that use the "heap" table access
method.  Sequences always use this table access method, but they do
not advertise as such in the pg_class system catalog, so the
aforementioned commit also (presumably unintentionally) removed
support for sequences from some of these functions.  This commit
reintroduces said support for sequences to these functions and adds
a couple of relevant tests.

Co-authored-by: Ayush Vatsa
Reviewed-by: Robert Haas, Michael Paquier, Matthias van de Meent
Discussion: https://postgr.es/m/CACX%2BKaP3i%2Bi9tdPLjF5JCHVv93xobEdcd_eB%2B638VDvZ3i%3DcQA%40mail.gmail.com
Backpatch-through: 12

6 files changed, 60 insertions, 2 deletions

diff --git a/contrib/pageinspect/expected/page.out b/contrib/pageinspect/expected/page.out
index 717ceccda37..a03fa5224d2 100644
--- a/contrib/pageinspect/expected/page.out
+++ b/contrib/pageinspect/expected/page.out
@@ -232,3 +232,12 @@ SELECT page_checksum(decode(repeat('00', :block_size), 'hex'), 1);
               
 (1 row)
 
+-- tests for sequences
+create temporary sequence test_sequence;
+select tuple_data_split('test_sequence'::regclass, t_data, t_infomask, t_infomask2, t_bits)
+  from heap_page_items(get_raw_page('test_sequence', 0));
+                   tuple_data_split                    
+-------------------------------------------------------
+ {"\\x0100000000000000","\\x0000000000000000","\\x00"}
+(1 row)
+
diff --git a/contrib/pageinspect/heapfuncs.c b/contrib/pageinspect/heapfuncs.c
index 11a910184bf..16a4a2233e5 100644
--- a/contrib/pageinspect/heapfuncs.c
+++ b/contrib/pageinspect/heapfuncs.c
@@ -318,7 +318,11 @@ tuple_data_split_internal(Oid relid, char *tupdata,
 	raw_attrs = initArrayResult(BYTEAOID, CurrentMemoryContext, false);
 	nattrs = tupdesc->natts;
 
-	if (rel->rd_rel->relam != HEAP_TABLE_AM_OID)
+	/*
+	 * Sequences always use heap AM, but they don't show that in the catalogs.
+	 */
+	if (rel->rd_rel->relkind != RELKIND_SEQUENCE &&
+		rel->rd_rel->relam != HEAP_TABLE_AM_OID)
 		ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 						errmsg("only heap AM is supported")));
 
diff --git a/contrib/pageinspect/sql/page.sql b/contrib/pageinspect/sql/page.sql
index 172f252638e..65dd931c45a 100644
--- a/contrib/pageinspect/sql/page.sql
+++ b/contrib/pageinspect/sql/page.sql
@@ -95,3 +95,8 @@ SHOW block_size \gset
 SELECT fsm_page_contents(decode(repeat('00', :block_size), 'hex'));
 SELECT page_header(decode(repeat('00', :block_size), 'hex'));
 SELECT page_checksum(decode(repeat('00', :block_size), 'hex'), 1);
+
+-- tests for sequences
+create temporary sequence test_sequence;
+select tuple_data_split('test_sequence'::regclass, t_data, t_infomask, t_infomask2, t_bits)
+  from heap_page_items(get_raw_page('test_sequence', 0));
diff --git a/contrib/pgstattuple/expected/pgstattuple.out b/contrib/pgstattuple/expected/pgstattuple.out
index 262633f0657..54a2faf7868 100644
--- a/contrib/pgstattuple/expected/pgstattuple.out
+++ b/contrib/pgstattuple/expected/pgstattuple.out
@@ -244,6 +244,30 @@ select pgstathashindex('test_partition_hash_idx');
  (4,8,0,1,0,0,0,100)
 (1 row)
 
+-- these should work for sequences
+create sequence test_sequence;
+select count(*) from pgstattuple('test_sequence');
+ count 
+-------
+     1
+(1 row)
+
+select pg_relpages('test_sequence');
+ pg_relpages 
+-------------
+           1
+(1 row)
+
+-- these should fail for sequences
+select pgstatindex('test_sequence');
+ERROR:  relation "test_sequence" is not a btree index
+select pgstatginindex('test_sequence');
+ERROR:  relation "test_sequence" is not a GIN index
+select pgstathashindex('test_sequence');
+ERROR:  relation "test_sequence" is not a hash index
+select pgstattuple_approx('test_sequence');
+ERROR:  "test_sequence" is not a table or materialized view
+drop sequence test_sequence;
 drop table test_partitioned;
 drop view test_view;
 drop foreign table test_foreign_table;
diff --git a/contrib/pgstattuple/pgstattuple.c b/contrib/pgstattuple/pgstattuple.c
index e524e1622c9..1c3c6c23a1e 100644
--- a/contrib/pgstattuple/pgstattuple.c
+++ b/contrib/pgstattuple/pgstattuple.c
@@ -335,7 +335,11 @@ pgstat_heap(Relation rel, FunctionCallInfo fcinfo)
 	pgstattuple_type stat = {0};
 	SnapshotData SnapshotDirty;
 
-	if (rel->rd_rel->relam != HEAP_TABLE_AM_OID)
+	/*
+	 * Sequences always use heap AM, but they don't show that in the catalogs.
+	 */
+	if (rel->rd_rel->relkind != RELKIND_SEQUENCE &&
+		rel->rd_rel->relam != HEAP_TABLE_AM_OID)
 		ereport(ERROR,
 				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 				 errmsg("only heap AM is supported")));
diff --git a/contrib/pgstattuple/sql/pgstattuple.sql b/contrib/pgstattuple/sql/pgstattuple.sql
index 6a6846fd9ae..2c19befe65f 100644
--- a/contrib/pgstattuple/sql/pgstattuple.sql
+++ b/contrib/pgstattuple/sql/pgstattuple.sql
@@ -114,6 +114,18 @@ create index test_partition_hash_idx on test_partition using hash (a);
 select pgstatindex('test_partition_idx');
 select pgstathashindex('test_partition_hash_idx');
 
+-- these should work for sequences
+create sequence test_sequence;
+select count(*) from pgstattuple('test_sequence');
+select pg_relpages('test_sequence');
+
+-- these should fail for sequences
+select pgstatindex('test_sequence');
+select pgstatginindex('test_sequence');
+select pgstathashindex('test_sequence');
+select pgstattuple_approx('test_sequence');
+
+drop sequence test_sequence;
 drop table test_partitioned;
 drop view test_view;
 drop foreign table test_foreign_table;