Subject: [PATCH v6] Fix 035_standby_logical_decoding.pl race condition

From: bdrouvot <[email-masked]>
Date: Tue, 9 Jan 2024 05:08:35 +0000

We want to ensure that vacuum was able to remove dead rows (aka no other
transactions holding back global xmin) before testing for slots invalidation on
the standby.
---
 .../t/035_standby_logical_decoding.pl         | 59 ++++++++++---------
 1 file changed, 30 insertions(+), 29 deletions(-)
 100.0% src/test/recovery/t/

diff --git a/src/test/recovery/t/035_standby_logical_decoding.pl b/src/test/recovery/t/035_standby_logical_decoding.pl
index 8bc39a5f03..9bfa8833b5 100644
--- a/src/test/recovery/t/035_standby_logical_decoding.pl
+++ b/src/test/recovery/t/035_standby_logical_decoding.pl
@@ -238,6 +238,25 @@ sub check_for_invalidation
 	) or die "Timed out waiting confl_active_logicalslot to be updated";
 }
 
+# Launch $sql and wait for a new snapshot that has a newer horizon before
+# doing the vacuum with $vac_option on $to_vac.
+sub wait_until_vacuum_can_remove
+{
+	my ($vac_option, $sql, $to_vac) = @_;
+
+	# get the current xid horizon
+	my $xid_horizon = $node_primary->safe_psql('testdb', qq[select pg_snapshot_xmin(pg_current_snapshot());]);
+
+	# launch our sql
+	$node_primary->safe_psql('testdb', qq[$sql]);
+
+	$node_primary->poll_query_until('testdb',
+		"SELECT (select pg_snapshot_xmin(pg_current_snapshot())::text::int - $xid_horizon) > 0")
+	  or die "new snapshot does not have a newer horizon";
+
+	$node_primary->safe_psql('testdb', qq[VACUUM $vac_option verbose $to_vac;
+										  INSERT INTO flush_wal DEFAULT VALUES; -- see create table flush_wal;]);
+}
 ########################
 # Initialize primary node
 ########################
@@ -248,6 +267,7 @@ $node_primary->append_conf(
 wal_level = 'logical'
 max_replication_slots = 4
 max_wal_senders = 4
+autovacuum = off
 });
 $node_primary->dump_info;
 $node_primary->start;
@@ -468,13 +488,8 @@ reactive_slots_change_hfs_and_wait_for_xmins('behaves_ok_', 'vacuum_full_',
 	0, 1);
 
 # This should trigger the conflict
-$node_primary->safe_psql(
-	'testdb', qq[
-  CREATE TABLE conflict_test(x integer, y text);
-  DROP TABLE conflict_test;
-  VACUUM full pg_class;
-  INSERT INTO flush_wal DEFAULT VALUES; -- see create table flush_wal
-]);
+wait_until_vacuum_can_remove('full', 'CREATE TABLE conflict_test(x integer, y text);
+								 DROP TABLE conflict_test;', 'pg_class');
 
 $node_primary->wait_for_replay_catchup($node_standby);
 
@@ -550,13 +565,8 @@ reactive_slots_change_hfs_and_wait_for_xmins('vacuum_full_', 'row_removal_',
 	0, 1);
 
 # This should trigger the conflict
-$node_primary->safe_psql(
-	'testdb', qq[
-  CREATE TABLE conflict_test(x integer, y text);
-  DROP TABLE conflict_test;
-  VACUUM pg_class;
-  INSERT INTO flush_wal DEFAULT VALUES; -- see create table flush_wal
-]);
+wait_until_vacuum_can_remove('', 'CREATE TABLE conflict_test(x integer, y text);
+							 DROP TABLE conflict_test;', 'pg_class');
 
 $node_primary->wait_for_replay_catchup($node_standby);
 
@@ -588,13 +598,8 @@ reactive_slots_change_hfs_and_wait_for_xmins('row_removal_',
 	'shared_row_removal_', 0, 1);
 
 # Trigger the conflict
-$node_primary->safe_psql(
-	'testdb', qq[
-  CREATE ROLE create_trash;
-  DROP ROLE create_trash;
-  VACUUM pg_authid;
-  INSERT INTO flush_wal DEFAULT VALUES; -- see create table flush_wal
-]);
+wait_until_vacuum_can_remove('', 'CREATE ROLE create_trash;
+							 DROP ROLE create_trash;', 'pg_authid');
 
 $node_primary->wait_for_replay_catchup($node_standby);
 
@@ -625,14 +630,10 @@ reactive_slots_change_hfs_and_wait_for_xmins('shared_row_removal_',
 	'no_conflict_', 0, 1);
 
 # This should not trigger a conflict
-$node_primary->safe_psql(
-	'testdb', qq[
-  CREATE TABLE conflict_test(x integer, y text);
-  INSERT INTO conflict_test(x,y) SELECT s, s::text FROM generate_series(1,4) s;
-  UPDATE conflict_test set x=1, y=1;
-  VACUUM conflict_test;
-  INSERT INTO flush_wal DEFAULT VALUES; -- see create table flush_wal
-]);
+wait_until_vacuum_can_remove('', 'CREATE TABLE conflict_test(x integer, y text);
+							 INSERT INTO conflict_test(x,y) SELECT s, s::text FROM generate_series(1,4) s;
+							 UPDATE conflict_test set x=1, y=1;', 'conflict_test');
+
 $node_primary->wait_for_replay_catchup($node_standby);
 
 # message should not be issued
-- 
2.34.1

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