Revert "Use WAIT FOR LSN in PostgreSQL::Test::Cluster::wait_for_catchup()"

This reverts commit f30848cb05d4d63e1a5a2d6a9d72604f3b63370d.  Due to
buildfarm failures related to recovery conflicts while executing the
WAIT FOR command.  It appears that WAIT FOR still holds xmin for a while.

Reported-by: Thomas Munro <thomas.munro@gmail.com>
Discussion: https://postgr.es/m/CA%2BhUKG%2BL0OQR8dQtsNBSaA3FNNyQeFabdeRVzurm0b7Xtp592g%40mail.gmail.com

diff --git a/src/test/perl/PostgreSQL/Test/Cluster.pm b/src/test/perl/PostgreSQL/Test/Cluster.pm
index a28ea89aa1019fe6dfe993635432424a90f2e4ff..955dfc0e7f81898cb102ab610a383e6f3e47b6e5 100644 (file)
--- a/src/test/perl/PostgreSQL/Test/Cluster.pm
+++ b/src/test/perl/PostgreSQL/Test/Cluster.pm
@@ -3320,13 +3320,6 @@ If you pass an explicit value of target_lsn, it should almost always be
 the primary's write LSN; so this parameter is seldom needed except when
 querying some intermediate replication node rather than the primary.
 
-When the standby is passed as a PostgreSQL::Test::Cluster instance and is
-in recovery, this function uses the WAIT FOR LSN command on the standby
-for modes replay, write, and flush.  This is more efficient than polling
-pg_stat_replication on the upstream, as WAIT FOR LSN uses a latch-based
-wakeup mechanism.  For 'sent' mode, or when the standby is passed as a
-string (e.g., a subscription name), it falls back to polling.
-
 If there is no active replication connection from this peer, waits until
 poll_query_until timeout.
 
@@ -3346,13 +3339,10 @@ sub wait_for_catchup
      . join(', ', keys(%valid_modes))
      unless exists($valid_modes{$mode});
 
-   # Keep a reference to the standby node if passed as an object, so we can
-   # use WAIT FOR LSN on it later.
-   my $standby_node;
+   # Allow passing of a PostgreSQL::Test::Cluster instance as shorthand
    if (blessed($standby_name)
        && $standby_name->isa("PostgreSQL::Test::Cluster"))
    {
-       $standby_node = $standby_name;
        $standby_name = $standby_name->name;
    }
    if (!defined($target_lsn))
@@ -3377,53 +3367,6 @@ sub wait_for_catchup
      . $self->name . "\n";
    # Before release 12 walreceiver just set the application name to
    # "walreceiver"
-
-   # Use WAIT FOR LSN on the standby when:
-   # - The standby was passed as a Cluster object (so we can connect to it)
-   # - The mode is replay, write, or flush (not 'sent')
-   # - The standby is in recovery
-   # This is more efficient than polling pg_stat_replication on the upstream,
-   # as WAIT FOR LSN uses a latch-based wakeup mechanism.
-   if (defined($standby_node) && ($mode ne 'sent'))
-   {
-       my $standby_in_recovery =
-         $standby_node->safe_psql('postgres', "SELECT pg_is_in_recovery()");
-       chomp($standby_in_recovery);
-
-       if ($standby_in_recovery eq 't')
-       {
-           # Map mode names to WAIT FOR LSN mode names
-           my %mode_map = (
-               'replay' => 'standby_replay',
-               'write' => 'standby_write',
-               'flush' => 'standby_flush',);
-           my $wait_mode = $mode_map{$mode};
-           my $timeout = $PostgreSQL::Test::Utils::timeout_default;
-           my $wait_query =
-             qq[WAIT FOR LSN '${target_lsn}' WITH (MODE '${wait_mode}', timeout '${timeout}s', no_throw);];
-           my $output = $standby_node->safe_psql('postgres', $wait_query);
-           chomp($output);
-
-           if ($output ne 'success')
-           {
-               # Fetch additional detail for debugging purposes
-               my $details = $self->safe_psql('postgres',
-                   "SELECT * FROM pg_catalog.pg_stat_replication");
-               diag qq(WAIT FOR LSN failed with status:
-   ${output});
-               diag qq(Last pg_stat_replication contents:
-   ${details});
-               croak "failed waiting for catchup";
-           }
-           print "done\n";
-           return;
-       }
-   }
-
-   # Fall back to polling pg_stat_replication on the upstream for:
-   # - 'sent' mode (no corresponding WAIT FOR LSN mode)
-   # - When standby_name is a string (e.g., subscription name)
-   # - When the standby is no longer in recovery (was promoted)
    my $query = qq[SELECT '$target_lsn' <= ${mode}_lsn AND state = 'streaming'
          FROM pg_catalog.pg_stat_replication
          WHERE application_name IN ('$standby_name', 'walreceiver')];