Fix race in test of pg_switch_wal().

The test failed when something added WAL between pg_switch_wal() and
pg_current_wal_lsn(), seen on buildfarm members hornet and sungazer.
Fix v10, v9.6 and v9.5 by making this code mirror its v13+ counterpart.
v12 and v11 lack a counterpart.

diff --git a/src/test/recovery/t/020_archive_status.pl b/src/test/recovery/t/020_archive_status.pl
index d79c0caf90835d280d52ea6d95ef80799de97766..b6912981027d64214a9f04d8869cd93460285a32 100644 (file)
--- a/src/test/recovery/t/020_archive_status.pl
+++ b/src/test/recovery/t/020_archive_status.pl
@@ -141,12 +141,14 @@ $primary->safe_psql(
    'postgres', q{
    INSERT INTO mine SELECT generate_series(21,30) AS x;
    CHECKPOINT;
-   SELECT pg_switch_wal();
 });
 
-# Make sure that the standby has caught here.
-my $primary_lsn = $primary->safe_psql('postgres',
-   q{SELECT pg_current_wal_lsn()});
+# Switch to a new segment and use the returned LSN to make sure that the
+# standby has caught up to this point.
+my $primary_lsn = $primary->safe_psql(
+   'postgres', q{
+   SELECT pg_switch_wal();
+});
 $standby1->poll_query_until('postgres',
    qq{ SELECT pg_wal_lsn_diff(pg_last_wal_replay_lsn(), '$primary_lsn') >= 0 },
    't')