fix-wait-for-catchup-default-behavior.patch

diff --git a/src/test/perl/PostgreSQL/Test/Cluster.pm b/src/test/perl/PostgreSQL/Test/Cluster.pm
index e18f27276c..fb6cc39db4 100644
--- a/src/test/perl/PostgreSQL/Test/Cluster.pm
+++ b/src/test/perl/PostgreSQL/Test/Cluster.pm
@@ -2509,8 +2509,10 @@ poll_query_until timeout.
 
 Requires that the 'postgres' db exists and is accessible.
 
-target_lsn may be any arbitrary lsn, but is typically $primary_node->lsn('insert').
-If omitted, pg_current_wal_lsn() is used.
+The default value of target_lsn is $node->lsn('write'), which ensures
+that the standby has caught up to what has been committed on the primary.
+Another plausible choice is $node->lsn('insert'), which ensures that
+preceding executed-but-not-committed WAL has been replayed as well.
 
 This is not a test. It die()s on failure.
 
@@ -2531,23 +2533,18 @@ sub wait_for_catchup
 	{
 		$standby_name = $standby_name->name;
 	}
-	my $lsn_expr;
-	if (defined($target_lsn))
+	if (!defined($target_lsn))
 	{
-		$lsn_expr = "'$target_lsn'";
-	}
-	else
-	{
-		$lsn_expr = 'pg_current_wal_lsn()';
+		$target_lsn = $self->lsn('write');
 	}
 	print "Waiting for replication conn "
 	  . $standby_name . "'s "
 	  . $mode
 	  . "_lsn to pass "
-	  . $lsn_expr . " on "
+	  . $target_lsn . " on "
 	  . $self->name . "\n";
 	my $query =
-	  qq[SELECT $lsn_expr <= ${mode}_lsn AND state = 'streaming' FROM pg_catalog.pg_stat_replication WHERE application_name = '$standby_name';];
+	  qq[SELECT '$target_lsn' <= ${mode}_lsn AND state = 'streaming' FROM pg_catalog.pg_stat_replication WHERE application_name = '$standby_name';];
 	$self->poll_query_until('postgres', $query)
 	  or croak "timed out waiting for catchup";
 	print "done\n";