[Bryan Green <dbryan.green@gmail.com>]

Greetings,

PostgreSQL::Test::Cluster::poll_query_until() accepts an undefined query 
for connection-only checks -- several recovery TAP tests call it that way:

     $node->poll_query_until('postgres', undef, '');


On timeout it builds a diag message that interpolates $query:

     diag qq(poll_query_until timed out executing this query:
     $query
     ...);

Cluster.pm runs under "use warnings FATAL => 'all'", so when $query is
undefined this does not warn, it dies with "Use of uninitialized value
$query in concatenation".  The result is that a timeout in a connection 
only poll fails with an uninitialized-value error instead of printing 
the timeout diagnostic the code is trying to produce, hiding the actual 
failure.

     $ perl -e 'use warnings FATAL => "all"; my $q; my $s = qq(q: $q);'
     Use of uninitialized value $q in concatenation (.) or string at -e 
line 1.

The fix uses a fallback string when the query is undefined:

     my $msg_query = $query // '(undef - connection attempt only)';

and interpolates $msg_query instead.  Test-only, one line.

--
Bryan Green
EDB: https://www.enterprisedb.com

Attachments:

0001-Avoid-uninitialized-value-error-in-poll_query_until-.patch (text/plain, 1.5K) download
From 114ae6240b1f35c31461228cc2af748bdf8813b9 Mon Sep 17 00:00:00 2001
From: Bryan Green <dbryan.green@gmail.com>
Date: Sat, 8 Aug 2026 15:27:42 -0500
Subject: [PATCH] Avoid uninitialized-value error in poll_query_until timeout
 diagnostic

PostgreSQL::Test::Cluster::poll_query_until() accepts an undefined query
for connection-only checks; several recovery TAP tests call it as
poll_query_until('postgres', undef, '').  On timeout it interpolates
$query into the diag message, and because Cluster.pm runs under
"use warnings FATAL => 'all'", interpolating the undefined value dies with
"Use of uninitialized value" instead of printing the intended diagnostic,
hiding the actual timeout.

Use a fallback string when the query is undefined.

Co-authored-by: Mark Dilger <mark.dilger@enterprisedb.com>
---
 src/test/perl/PostgreSQL/Test/Cluster.pm | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/test/perl/PostgreSQL/Test/Cluster.pm b/src/test/perl/PostgreSQL/Test/Cluster.pm
index 3eae4cf628..9fec6b4e42 100644
--- a/src/test/perl/PostgreSQL/Test/Cluster.pm
+++ b/src/test/perl/PostgreSQL/Test/Cluster.pm
@@ -2808,8 +2808,9 @@ sub poll_query_until
 
 	# Give up. Print the output from the last attempt, hopefully that's useful
 	# for debugging.
+	my $msg_query = $query // '(undef - connection attempt only)';
 	diag qq(poll_query_until timed out executing this query:
-$query
+$msg_query
 expecting this output:
 $expected
 last actual query output:
-- 
2.49.0