From 0f5e1efad7f513dc225f1aff06f33f2b9ad99b1a Mon Sep 17 00:00:00 2001
From: Robert Haas <rhaas@postgresql.org>
Date: Tue, 8 Jun 2021 14:31:22 -0400
Subject: [PATCH v7 1/2] Back-port a few PostgresNode.pm methods.

The 'lsn' and 'wait_for_catchup' methods only exist in v10 and
higher, but are needed in order to support a test planned test
case for a bug that exists all the way back to v9.6. To minimize
cross-branch differences in the test case, back-port these
methods.

Discussion: http://postgr.es/m/CA+TgmoaG5dmA_8Xc1WvbvftPjtwx5uzkGEHxE7MiJ+im9jynmw@mail.gmail.com
---
 src/test/perl/PostgresNode.pm | 83 +++++++++++++++++++++++++++++++++++
 1 file changed, 83 insertions(+)

diff --git a/src/test/perl/PostgresNode.pm b/src/test/perl/PostgresNode.pm
index 5c5926559d..5f5a7d2731 100644
--- a/src/test/perl/PostgresNode.pm
+++ b/src/test/perl/PostgresNode.pm
@@ -1472,6 +1472,89 @@ sub issues_sql_like
 
 =pod
 
+=item $node->lsn(mode)
+
+Look up WAL locations on the server:
+
+ * insert location (master only, error on replica)
+ * write location (master only, error on replica)
+ * flush location (master only, error on replica)
+ * receive location (always undef on master)
+ * replay location (always undef on master)
+
+mode must be specified.
+
+=cut
+
+sub lsn
+{
+	my ($self, $mode) = @_;
+	my %modes = (
+		'insert'  => 'pg_current_xlog_insert_location()',
+		'flush'   => 'pg_current_xlog_flush_location()',
+		'write'   => 'pg_current_xlog_location()',
+		'receive' => 'pg_last_xlog_receive_location()',
+		'replay'  => 'pg_last_xlog_replay_location()');
+
+	$mode = '<undef>' if !defined($mode);
+	die "unknown mode for 'lsn': '$mode', valid modes are "
+	  . join(', ', keys %modes)
+	  if !defined($modes{$mode});
+
+	my $result = $self->safe_psql('postgres', "SELECT $modes{$mode}");
+	chomp($result);
+	if ($result eq '')
+	{
+		return;
+	}
+	else
+	{
+		return $result;
+	}
+}
+
+=pod
+
+=item $node->wait_for_catchup(standby_name, mode, target_lsn)
+
+Wait for the node with application_name standby_name (usually from node->name)
+until its replication position in pg_stat_replication equals or passes the
+upstream's xlog insert point at the time this function is called. By default
+the replay_location is waited for, but 'mode' may be specified to wait for any
+of sent|write|flush|replay.
+
+If there is no active replication connection from this peer, waits until
+poll_query_until timeout.
+
+Requires that the 'postgres' db exists and is accessible.
+
+target_lsn may be any arbitrary lsn, but is typically $master_node->lsn('insert').
+
+This is not a test. It die()s on failure.
+
+=cut
+
+sub wait_for_catchup
+{
+	my ($self, $standby_name, $mode, $target_lsn) = @_;
+	$mode = defined($mode) ? $mode : 'replay';
+	my %valid_modes = ( 'sent' => 1, 'write' => 1, 'flush' => 1, 'replay' => 1 );
+	die "unknown mode $mode for 'wait_for_catchup', valid modes are " . join(', ', keys(%valid_modes)) unless exists($valid_modes{$mode});
+	# Allow passing of a PostgresNode instance as shorthand
+	if ( blessed( $standby_name ) && $standby_name->isa("PostgresNode") )
+	{
+		$standby_name = $standby_name->name;
+	}
+	die 'target_lsn must be specified' unless defined($target_lsn);
+	print "Waiting for replication conn " . $standby_name . "'s " . $mode . "_location to pass " . $target_lsn . " on " . $self->name . "\n";
+	my $query = qq[SELECT '$target_lsn' <= ${mode}_location FROM pg_catalog.pg_stat_replication WHERE application_name = '$standby_name';];
+	$self->poll_query_until('postgres', $query)
+		or die "timed out waiting for catchup, current position is " . ($self->safe_psql('postgres', $query) || '(unknown)');
+	print "done\n";
+}
+
+=pod
+
 =back
 
 =cut
-- 
2.24.3 (Apple Git-128)