From ed4c75ee737af29b28dcbb635c17a54531bd5a19 Mon Sep 17 00:00:00 2001 From: Manu Date: Sat, 17 Oct 2026 01:24:07 -0300 Subject: [PATCH v2] pg_upgrade: Don't store an invalid datminmxid/relminmxid If the old cluster's newest multixid was the last one before multixid wraparound (0xFFFFFFFF), its checkpoint records NextMultiXactId = 0: servers before v19 skip 0 only when the next multixid is assigned. copy_xact_xlog_xid() already turns that into FirstMultiXactId before passing it to pg_resetwal, but set_frozenxids() stored the raw 0 in pg_database.datminmxid and in pg_class.relminmxid of the initdb-created tables. In assert-enabled builds the next VACUUM then fails an assertion; otherwise template0 keeps datminmxid = 0, mxid_age() reports 2147483647 for it, and VACUUM logs "cannot truncate up to MultiXact 0 because it has invalid offset, skipping truncation". Apply the same adjustment in set_frozenxids(). --- src/bin/pg_upgrade/pg_upgrade.c | 16 ++++- .../pg_upgrade/t/007_multixact_conversion.pl | 59 +++++++++++++++++++ 2 files changed, 73 insertions(+), 2 deletions(-) diff --git a/src/bin/pg_upgrade/pg_upgrade.c b/src/bin/pg_upgrade/pg_upgrade.c index 6d01084..72530b7 100644 --- a/src/bin/pg_upgrade/pg_upgrade.c +++ b/src/bin/pg_upgrade/pg_upgrade.c @@ -913,9 +913,21 @@ set_frozenxids(void) int ntups; int i_datname; int i_datallowconn; + MultiXactId minmxid; prep_status("Setting frozenxid and minmxid counters in new cluster"); + /* + * The old cluster's next multixid is 0 if its newest multixid was the + * last one before wraparound, because servers before v19 skip 0 only when + * assigning the next one. 0 is not a valid multixid, so use the value + * that it will have when the next multixid is assigned, the same that + * copy_xact_xlog_xid() passes to pg_resetwal. + */ + minmxid = old_cluster.controldata.chkpnt_nxtmulti; + if (minmxid < FirstMultiXactId) + minmxid = FirstMultiXactId; + conn_template1 = connectToServer(&new_cluster, "template1"); /* set pg_database.datfrozenxid */ @@ -928,7 +940,7 @@ set_frozenxids(void) PQclear(executeQueryOrDie(conn_template1, "UPDATE pg_catalog.pg_database " "SET datminmxid = '%u'", - old_cluster.controldata.chkpnt_nxtmulti)); + minmxid)); /* get database names */ dbres = executeQueryOrDie(conn_template1, @@ -978,7 +990,7 @@ set_frozenxids(void) CppAsString2(RELKIND_RELATION) ", " CppAsString2(RELKIND_MATVIEW) ", " CppAsString2(RELKIND_TOASTVALUE) ")", - old_cluster.controldata.chkpnt_nxtmulti)); + minmxid)); PQfinish(conn); /* Reset datallowconn flag */ diff --git a/src/bin/pg_upgrade/t/007_multixact_conversion.pl b/src/bin/pg_upgrade/t/007_multixact_conversion.pl index 5c87c25..4cc7e1b 100644 --- a/src/bin/pg_upgrade/t/007_multixact_conversion.pl +++ b/src/bin/pg_upgrade/t/007_multixact_conversion.pl @@ -484,4 +484,63 @@ SKIP: upgrade_and_compare($tag, $old, $new); } +# Multixid wraparound at the last multixid: The newest multixid is +# 0xFFFFFFFF, so the old cluster's next multixid is 0. That must not +# end up as datminmxid or relminmxid in the new cluster. +SKIP: +{ + skip + "skipping mxid wraparound tests because upgrading from the old version does not require conversion" + if ($old_version >= '19devel'); + + my $tag = 'last_mxid'; + my $old = + PostgreSQL::Test::Cluster->new("${tag}_oldnode", + install_path => $ENV{oldinstall}); + my $new = PostgreSQL::Test::Cluster->new("${tag}_newnode"); + + $old->init(extra => ['-k']); + + reset_mxid_mxoffset_pre_v19($old, 0xFFFFFFFF, 0x10000); + + # Create one multixid with two members, a locker and an updater + $old->start; + $old->safe_psql( + 'postgres', qq[ + CREATE TABLE mxofftest (id INT PRIMARY KEY, n_updated INT) + WITH (AUTOVACUUM_ENABLED=FALSE); + INSERT INTO mxofftest SELECT G, 0 FROM GENERATE_SERIES(1, 2) G; + ]); + my $locker = + $new->background_psql('', connstr => $old->connstr('postgres')); + $locker->query_safe("BEGIN"); + $locker->query_safe("SELECT * FROM mxofftest WHERE id = 1 FOR KEY SHARE"); + $old->safe_psql('postgres', + "UPDATE mxofftest SET n_updated = n_updated + 1 WHERE id = 1"); + $locker->query_safe("COMMIT"); + $locker->quit; + $old->stop; + + my (undef, $next_mxid, undef) = read_multixid_fields($old); + is($next_mxid, 0, "next multixid wrapped around to 0 in old cluster"); + + $new->init; + upgrade_and_compare($tag, $old, $new); + + $new->start; + is( $new->safe_psql( + 'postgres', + "SELECT count(*) FROM pg_database WHERE datminmxid = '0'"), + '0', + 'no database has an invalid datminmxid after upgrade'); + is( $new->safe_psql( + 'postgres', + "SELECT count(*) FROM pg_class WHERE relminmxid = '0' AND relkind IN ('r', 'm', 't')" + ), + '0', + 'no table has an invalid relminmxid after upgrade'); + $new->safe_psql('postgres', 'VACUUM'); + $new->stop; +} + done_testing(); -- 2.56.0