Support amcheck of sequences

Sequences were left out of the list of relation kinds that
verify_heapam knew how to check, though it is fairly trivial to allow
them.  Doing that, and while at it, updating pg_amcheck to include
sequences in relations matched by table and relation patterns.

Author: Mark Dilger <mark.dilger@enterprisedb.com>
Discussion: https://www.postgresql.org/message-id/flat/81ad4757-92c1-4aa3-7bee-f609544837e3%40enterprisedb.com

contrib/amcheck/expected/check_heap.out

@@ -180,8 +180,10 @@ CREATE SEQUENCE test_sequence;
 SELECT * FROM verify_heapam('test_sequence',
 							startblock := NULL,
 							endblock := NULL);
-ERROR:  cannot check relation "test_sequence"
-DETAIL:  This operation is not supported for sequences.
+ blkno | offnum | attnum | msg 
+-------+--------+--------+-----
+(0 rows)
+
 -- Check that foreign tables are rejected
 CREATE FOREIGN DATA WRAPPER dummy;
 CREATE SERVER dummy_server FOREIGN DATA WRAPPER dummy;

contrib/amcheck/t/001_verify_heapam.pl

@@ -8,7 +8,7 @@ use PostgresNode;
 use TestLib;
 
 use Fcntl qw(:seek);
-use Test::More tests => 80;
+use Test::More tests => 272;
 
 my ($node, $result);
 
@@ -60,6 +60,22 @@ detects_no_corruption(
 	"verify_heapam('test', skip := 'all-frozen')",
 	"all-frozen corrupted table skipping all-frozen");
 
+#
+# Check a sequence with no corruption.  The current implementation of sequences
+# doesn't require its own test setup, since sequences are really just heap
+# tables under-the-hood.  To guard against future implementation changes made
+# without remembering to update verify_heapam, we create and exercise a
+# sequence, checking along the way that it passes corruption checks.
+#
+fresh_test_sequence('test_seq');
+check_all_options_uncorrupted('test_seq', 'plain');
+advance_test_sequence('test_seq');
+check_all_options_uncorrupted('test_seq', 'plain');
+set_test_sequence('test_seq');
+check_all_options_uncorrupted('test_seq', 'plain');
+reset_test_sequence('test_seq');
+check_all_options_uncorrupted('test_seq', 'plain');
+
 # Returns the filesystem path for the named relation.
 sub relation_filepath
 {
@@ -110,6 +126,56 @@ sub fresh_test_table
 	));
 }
 
+# Create a test sequence of the given name.
+sub fresh_test_sequence
+{
+	my ($seqname) = @_;
+
+	return $node->safe_psql(
+		'postgres', qq(
+		DROP SEQUENCE IF EXISTS $seqname CASCADE;
+		CREATE SEQUENCE $seqname
+			INCREMENT BY 13
+			MINVALUE 17
+			START WITH 23;
+		SELECT nextval('$seqname');
+		SELECT setval('$seqname', currval('$seqname') + nextval('$seqname'));
+	));
+}
+
+# Call SQL functions to increment the sequence
+sub advance_test_sequence
+{
+	my ($seqname) = @_;
+
+	return $node->safe_psql(
+		'postgres', qq(
+		SELECT nextval('$seqname');
+	));
+}
+
+# Call SQL functions to set the sequence
+sub set_test_sequence
+{
+	my ($seqname) = @_;
+
+	return $node->safe_psql(
+		'postgres', qq(
+		SELECT setval('$seqname', 102);
+	));
+}
+
+# Call SQL functions to reset the sequence
+sub reset_test_sequence
+{
+	my ($seqname) = @_;
+
+	return $node->safe_psql(
+		'postgres', qq(
+		ALTER SEQUENCE $seqname RESTART WITH 51
+	));
+}
+
 # Stops the test node, corrupts the first page of the named relation, and
 # restarts the node.
 sub corrupt_first_page

contrib/amcheck/verify_heapam.c

@@ -305,14 +305,20 @@ verify_heapam(PG_FUNCTION_ARGS)
 	 */
 	if (ctx.rel->rd_rel->relkind != RELKIND_RELATION &&
 		ctx.rel->rd_rel->relkind != RELKIND_MATVIEW &&
-		ctx.rel->rd_rel->relkind != RELKIND_TOASTVALUE)
+		ctx.rel->rd_rel->relkind != RELKIND_TOASTVALUE &&
+		ctx.rel->rd_rel->relkind != RELKIND_SEQUENCE)
 		ereport(ERROR,
 				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
 				 errmsg("cannot check relation \"%s\"",
 						RelationGetRelationName(ctx.rel)),
 				 errdetail_relkind_not_supported(ctx.rel->rd_rel->relkind)));
 
-	if (ctx.rel->rd_rel->relam != HEAP_TABLE_AM_OID)
+	/*
+	 * Sequences always use heap AM, but they don't show that in the catalogs.
+	 * Other relkinds might be using a different AM, so check.
+	 */
+	if (ctx.rel->rd_rel->relkind != RELKIND_SEQUENCE &&
+		ctx.rel->rd_rel->relam != HEAP_TABLE_AM_OID)
 		ereport(ERROR,
 				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 				 errmsg("only heap AM is supported")));