From f9d9641d6612fdc3f44da9cfe388658f8417fcb4 Mon Sep 17 00:00:00 2001 From: Melanie Plageman Date: Tue, 13 Oct 2026 14:50:04 -0400 Subject: [PATCH v5] Forget invalid VM pages during truncation replay Commit ed62d26caca made heap records that clear visibility map bits register VM blocks, causing redo to read those blocks with RBM_NORMAL. If such a record is replayed after the VM fork was already truncated on disk, recovery records a missing-page reference. Replaying the truncation only forgot missing pages from the main fork, so recovery later PANICs with unresolved invalid pages. Call XLogTruncateRelation() for the VM fork when replaying a VM truncation. Reported-by: Jacky Nguyen Reviewed-by: Kirill Reshke Reviewed-by: Shihao Zhong Reviewed-by: Rahul Yadav Discussion: https://postgr.es/m/CAL4mQLAp562c1rCgg2Dqx6TBSdOk6vOvaLFjwFG9E6k4uwvJJw%40mail.gmail.com Backpatch-through: 17 --- .../t/001_concurrent_transaction.pl | 49 +++++++++++++++++++ src/backend/catalog/storage.c | 12 ++++- 2 files changed, 59 insertions(+), 2 deletions(-) diff --git a/contrib/pg_visibility/t/001_concurrent_transaction.pl b/contrib/pg_visibility/t/001_concurrent_transaction.pl index 9911720984e..6df434bf5d4 100644 --- a/contrib/pg_visibility/t/001_concurrent_transaction.pl +++ b/contrib/pg_visibility/t/001_concurrent_transaction.pl @@ -3,6 +3,9 @@ # Check that a concurrent transaction doesn't cause false negatives in # pg_check_visible() function +# +# Also check that a standby can restart after replaying a VM clear followed by +# a VM truncation. use strict; use warnings FATAL => 'all'; use PostgreSQL::Test::Cluster; @@ -13,6 +16,11 @@ use Test::More; # Initialize the primary node my $node = PostgreSQL::Test::Cluster->new('main'); $node->init(allows_streaming => 1); +$node->append_conf( + 'postgresql.conf', qq{ +autovacuum = off +checkpoint_timeout = 1h +}); $node->start; # Initialize the streaming standby @@ -57,6 +65,47 @@ ok($result eq "", "pg_check_visible() detects no errors"); # Shutdown $bsession->query_safe("COMMIT;"); $bsession->quit; + +# A WAL record clearing a VM bit registers the VM block. Make sure a standby +# that crashes after the VM fork was truncated, and so replays the clear again +# against a missing VM block, doesn't leave an unresolved invalid-page +# reference behind: the VM truncation record must forget it. +$node->safe_psql( + "postgres", + "CREATE TABLE vm_truncate_test AS SELECT generate_series(1, 500) i;\n" + . "VACUUM (FREEZE) vm_truncate_test;"); + +# Move the standby's restart point past the VM set but before the VM clear. +$node->safe_psql("postgres", "CHECKPOINT;"); +$node->wait_for_catchup($standby); +$standby->safe_psql("postgres", "CHECKPOINT;"); + +# Without full page images, the VM clear is replayed as a plain delta. +$node->append_conf('postgresql.conf', "full_page_writes = off"); +$node->reload; +$node->poll_query_until( + "postgres", + q{SELECT current_setting('full_page_writes') = 'off';}); + +$node->safe_psql( + "postgres", + "UPDATE vm_truncate_test SET i = 0 WHERE i = 1;\n" + . "SELECT pg_truncate_visibility_map('vm_truncate_test');"); +$node->wait_for_catchup($standby); + +is( $standby->safe_psql( + "postgres", "SELECT pg_relation_size('vm_truncate_test', 'vm');"), + '0', + "VM fork truncated on standby"); + +# Crash the standby; redo restarts before the VM clear. +$standby->stop('immediate'); +my $log_offset = -s $standby->logfile; +ok($standby->start(fail_ok => 1), "standby restarts after VM truncation"); +ok( !$standby->log_contains( + qr/WAL contains references to invalid pages/, $log_offset), + "no invalid-page PANIC during recovery"); + $node->stop; $standby->stop; diff --git a/src/backend/catalog/storage.c b/src/backend/catalog/storage.c index 85d1219b235..3533ca7fcfa 100644 --- a/src/backend/catalog/storage.c +++ b/src/backend/catalog/storage.c @@ -1059,10 +1059,18 @@ smgr_redo(XLogReaderState *record) need_fsm_vacuum = true; } } - if ((xlrec->flags & SMGR_TRUNCATE_VM) != 0 && - smgrexists(reln, VISIBILITYMAP_FORKNUM)) + if ((xlrec->flags & SMGR_TRUNCATE_VM) != 0) { + /* + * Also tell xlogutils.c about it. Do this even if the VM fork is + * already short enough (e.g. replaying again after a crash), as + * earlier records may have logged invalid pages for it. + */ + XLogTruncateRelation(xlrec->rlocator, VISIBILITYMAP_FORKNUM, + visibilitymap_truncation_length(xlrec->blkno)); + blocks[nforks] = visibilitymap_prepare_truncate(rel, xlrec->blkno); + if (BlockNumberIsValid(blocks[nforks])) { forks[nforks] = VISIBILITYMAP_FORKNUM; -- 2.43.0