Support RBM_ZERO_AND_CLEANUP_LOCK in ExtendBufferedRelTo(), add tests

For some reason I had not implemented RBM_ZERO_AND_CLEANUP_LOCK support in
ExtendBufferedRelTo(), likely thinking it not being reachable. But it is
reachable, e.g. when replaying a WAL record for a page in a relation that
subsequently is truncated (likely only reachable when doing crash recovery or
PITR, not during ongoing streaming replication).

As now all of the RBM_* modes are supported, remove assertions checking mode.

As we had no test coverage for this scenario, add a new TAP test. There's
plenty more that ought to be tested in this area...

Reported-by: Tom Lane <tgl@sss.pgh.pa.us>
Reported-by: Alexander Lakhin <exclusion@gmail.com>
Reviewed-by: Alexander Lakhin <exclusion@gmail.com>
Discussion: https://postgr.es/m/392271.1681238924%40sss.pgh.pa.us
Discussion: https://postgr.es/m/0b5eb82b-cb99-e0a4-b932-3dc60e2e3926@gmail.com

2 files changed, 137 insertions, 0 deletions

diff --git a/src/test/recovery/meson.build b/src/test/recovery/meson.build
index e834ad5e0d..2008958010 100644
--- a/src/test/recovery/meson.build
+++ b/src/test/recovery/meson.build
@@ -41,6 +41,7 @@ tests += {
       't/033_replay_tsp_drops.pl',
       't/034_create_database.pl',
       't/035_standby_logical_decoding.pl',
+      't/036_truncated_dropped.pl',
     ],
   },
 }
diff --git a/src/test/recovery/t/036_truncated_dropped.pl b/src/test/recovery/t/036_truncated_dropped.pl
new file mode 100644
index 0000000000..2d5339d9d8
--- /dev/null
+++ b/src/test/recovery/t/036_truncated_dropped.pl
@@ -0,0 +1,136 @@
+# Copyright (c) 2021-2023, PostgreSQL Global Development Group
+
+# Tests recovery scenarios where the files are shorter than in the common
+# cases, e.g. due to replaying WAL records of a relation that was subsequently
+# truncated or dropped.
+
+use strict;
+use warnings;
+use PostgreSQL::Test::Cluster;
+use Test::More;
+
+my $node = PostgreSQL::Test::Cluster->new('n1');
+
+$node->init();
+
+# Disable autovacuum to guarantee VACUUM can remove rows / truncate relations
+$node->append_conf(
+	'postgresql.conf', qq[
+wal_level = 'replica'
+autovacuum = off
+]);
+
+$node->start();
+
+
+# Test: Replay replay of PRUNE records for a pre-existing, then dropped,
+# relation
+
+$node->safe_psql(
+	'postgres', qq[
+CREATE TABLE truncme(i int) WITH (fillfactor = 50);
+INSERT INTO truncme SELECT generate_series(1, 1000);
+UPDATE truncme SET i = 1;
+CHECKPOINT; -- ensure relation exists at start of recovery
+VACUUM truncme; -- generate prune records
+DROP TABLE truncme;
+]);
+
+$node->stop('immediate');
+
+ok($node->start(),
+	'replay of PRUNE records for a pre-existing, then dropped, relation');
+
+
+# Test: Replay of PRUNE records for a newly created, then dropped, relation
+
+$node->safe_psql(
+	'postgres', qq[
+CREATE TABLE truncme(i int) WITH (fillfactor = 50);
+INSERT INTO truncme SELECT generate_series(1, 1000);
+UPDATE truncme SET i = 1;
+VACUUM truncme; -- generate prune records
+DROP TABLE truncme;
+]);
+
+$node->stop('immediate');
+
+ok($node->start(),
+	'replay of PRUNE records for a newly created, then dropped, relation');
+
+
+# Test: Replay of PRUNE records affecting truncated block. With FPIs used for
+# PRUNE.
+
+$node->safe_psql(
+	'postgres', qq[
+CREATE TABLE truncme(i int) WITH (fillfactor = 50);
+INSERT INTO truncme SELECT generate_series(1, 1000);
+UPDATE truncme SET i = 1;
+CHECKPOINT; -- generate FPIs
+VACUUM truncme; -- generate prune records
+TRUNCATE truncme; -- make blocks non-existing
+INSERT INTO truncme SELECT generate_series(1, 10);
+]);
+
+$node->stop('immediate');
+
+ok($node->start(),
+	'replay of PRUNE records affecting truncated block (FPIs)');
+
+is($node->safe_psql('postgres', 'select count(*), sum(i) FROM truncme'),
+	'10|55', 'table contents as expected after recovery');
+$node->safe_psql('postgres', 'DROP TABLE truncme');
+
+
+# Test replay of PRUNE records for blocks that are later truncated. Without
+# FPIs used for PRUNE.
+
+$node->safe_psql(
+	'postgres', qq[
+CREATE TABLE truncme(i int) WITH (fillfactor = 50);
+INSERT INTO truncme SELECT generate_series(1, 1000);
+UPDATE truncme SET i = 1;
+VACUUM truncme; -- generate prune records
+TRUNCATE truncme; -- make blocks non-existing
+INSERT INTO truncme SELECT generate_series(1, 10);
+]);
+
+$node->stop('immediate');
+
+ok($node->start(),
+	'replay of PRUNE records affecting truncated block (no FPIs)');
+
+is($node->safe_psql('postgres', 'select count(*), sum(i) FROM truncme'),
+	'10|55', 'table contents as expected after recovery');
+$node->safe_psql('postgres', 'DROP TABLE truncme');
+
+
+# Test: Replay of partial truncation via VACUUM
+
+$node->safe_psql(
+	'postgres', qq[
+CREATE TABLE truncme(i int) WITH (fillfactor = 50);
+INSERT INTO truncme SELECT generate_series(1, 1000);
+UPDATE truncme SET i = i + 1;
+-- ensure a mix of pre/post truncation rows
+DELETE FROM truncme WHERE i > 500;
+
+VACUUM truncme; -- should truncate relation
+
+-- rows at TIDs that previously existed
+INSERT INTO truncme SELECT generate_series(1000, 1010);
+]);
+
+$node->stop('immediate');
+
+ok($node->start(), 'replay of partial truncation via VACUUM');
+
+is( $node->safe_psql(
+		'postgres', 'select count(*), sum(i), min(i), max(i) FROM truncme'),
+	'510|136304|2|1010',
+	'table contents as expected after recovery');
+$node->safe_psql('postgres', 'DROP TABLE truncme');
+
+
+done_testing();