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amcheck: Distinguish interrupted page deletion from corruption.

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This prevents false-positive reports about "the first child of leftmost
target page is not leftmost of its level", "block %u is not leftmost"
and "left link/right link pair".  They appeared if amcheck ran before
VACUUM cleaned things, after a cluster exited recovery between the
first-stage and second-stage WAL records of a deletion.  Back-patch to
v11 (all supported versions).

Reviewed by Peter Geoghegan.

Discussion: https://postgr.es/m/20231005025232.c7.nmisch@google.com
This commit is contained in:
Noah Misch
2023-10-30 14:46:05 -07:00
parent 56b30e266e
commit 6ec9e9975e
4 changed files with 163 additions and 4 deletions
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82
contrib/amcheck/t/005_pitr.pl Normal file
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# Copyright (c) 2021-2023, PostgreSQL Global Development Group
# Test integrity of intermediate states by PITR to those states
use strict;
use warnings;
use PostgreSQL::Test::Cluster;
use PostgreSQL::Test::Utils;
use Test::More;
# origin node: generate WAL records of interest.
my $origin = PostgreSQL::Test::Cluster->new('origin');
$origin->init(has_archiving => 1, allows_streaming => 1);
$origin->append_conf('postgresql.conf', 'autovacuum = off');
$origin->start;
$origin->backup('my_backup');
# Create a table with each of 6 PK values spanning 1/4 of a block. Delete the
# first four, so one index leaf is eligible for deletion. Make a replication
# slot just so pg_walinspect will always have access to later WAL.
my $setup = <<EOSQL;
BEGIN;
CREATE EXTENSION amcheck;
CREATE EXTENSION pg_walinspect;
CREATE TABLE not_leftmost (c text STORAGE PLAIN);
INSERT INTO not_leftmost
SELECT repeat(n::text, database_block_size / 4)
FROM generate_series(1,6) t(n), pg_control_init();
ALTER TABLE not_leftmost ADD CONSTRAINT not_leftmost_pk PRIMARY KEY (c);
DELETE FROM not_leftmost WHERE c ~ '^[1-4]';
SELECT pg_create_physical_replication_slot('for_walinspect', true, false);
COMMIT;
EOSQL
$origin->safe_psql('postgres', $setup);
my $before_vacuum_lsn =
$origin->safe_psql('postgres', "SELECT pg_current_wal_lsn()");
# VACUUM to delete the aforementioned leaf page. Force an XLogFlush() by
# dropping a permanent table. That way, the XLogReader infrastructure can
# always see VACUUM's records, even under synchronous_commit=off. Finally,
# find the LSN of that VACUUM's last UNLINK_PAGE record.
my $vacuum = <<EOSQL;
SET synchronous_commit = off;
VACUUM (VERBOSE, INDEX_CLEANUP ON) not_leftmost;
CREATE TABLE XLogFlush ();
DROP TABLE XLogFlush;
SELECT max(start_lsn)
FROM pg_get_wal_records_info('$before_vacuum_lsn', 'FFFFFFFF/FFFFFFFF')
WHERE resource_manager = 'Btree' AND record_type = 'UNLINK_PAGE';
EOSQL
my $unlink_lsn = $origin->safe_psql('postgres', $vacuum);
$origin->stop;
die "did not find UNLINK_PAGE record" unless $unlink_lsn;
# replica node: amcheck at notable points in the WAL stream
my $replica = PostgreSQL::Test::Cluster->new('replica');
$replica->init_from_backup($origin, 'my_backup', has_restoring => 1);
$replica->append_conf('postgresql.conf',
"recovery_target_lsn = '$unlink_lsn'");
$replica->append_conf('postgresql.conf', 'recovery_target_inclusive = off');
$replica->append_conf('postgresql.conf', 'recovery_target_action = promote');
$replica->start;
$replica->poll_query_until('postgres', "SELECT pg_is_in_recovery() = 'f';")
or die "Timed out while waiting for PITR promotion";
# recovery done; run amcheck
my $debug = "SET client_min_messages = 'debug1'";
my ($rc, $stderr);
$rc = $replica->psql(
'postgres',
"$debug; SELECT bt_index_parent_check('not_leftmost_pk', true)",
stderr => \$stderr);
print STDERR $stderr, "\n";
is($rc, 0, "bt_index_parent_check passes");
like(
$stderr,
qr/interrupted page deletion detected/,
"bt_index_parent_check: interrupted page deletion detected");
$rc = $replica->psql(
'postgres',
"$debug; SELECT bt_index_check('not_leftmost_pk', true)",
stderr => \$stderr);
print STDERR $stderr, "\n";
is($rc, 0, "bt_index_check passes");
done_testing();