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commit    a5447a2deaca65c69f1838240f6bdb3ff85c9577
Author:   Daniel Gustafsson <dgustafsson@postgresql.org>
Date:     Mon Sep 28 15:46:56 2026 +0000

    Fix WAL file selection in 013_rewind test
    
    Without an explicit WAL filename, pg_waldump determines the segment
    size from the first WAL-named directory entry.  A preallocated
    segment with an uninitialized header can make this fail before the
    checkpoint is read.
    
    Pass the WAL filename recorded in backup_label to avoid depending
    on directory enumeration order.  Use command_like() so command
    failures and stderr are checked rather than appearing only as an
    empty-output mismatch.
    
    This was independently reported by Nazir Bilal Yavuz and Alexander
    Lakhin.
    
    Author: Nazir Bilal Yavuz <byavuz81@gmail.com>
    Reported-by: Nazir Bilal Yavuz <byavuz81@gmail.com>
    Reported-by: Alexander Lakhin <exclusion@gmail.com>
    Reviewed-by: Zsolt Parragi <zsolt.parragi@percona.com>
    Reviewed-by: Daniel Gustafsson <daniel@yesql.se>
    Discussion: https://postgr.es/m/CAN55FZ1Yak_xBqMaDQsD7atpBkGLEkF-DKXcs3nLHM1Uq4YRew%40mail.gmail.com
    Discussion: https://postgr.es/m/ffd837c5-dc22-4db1-a2d8-b623cbe9b30c@gmail.com


 src/test/modules/test_checksums/t/013_rewind.pl | 20 ++++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

diff --git a/src/test/modules/test_checksums/t/013_rewind.pl b/src/test/modules/test_checksums/t/013_rewind.pl
index 21715ace9f3..2cf411e9115 100644
--- a/src/test/modules/test_checksums/t/013_rewind.pl
+++ b/src/test/modules/test_checksums/t/013_rewind.pl
@@ -151,15 +151,27 @@ $backup_label =~ /^CHECKPOINT LOCATION: ([0-9A-F\/]+)$/m
   or die "checkpoint location missing from backup_label";
 is($1, $shutdown_ckpt, 'replay starts at the switchover checkpoint');
 
-($stdout, $stderr) = run_command(
+# Specify the WAL file so that pg_waldump does not try to determine the
+# segment size from an arbitrary, possibly preallocated, file in pg_wal.
+# This test would fail if the checkpoint record is straddling two WAL
+# segments, if this is ever observed then support for reading the next
+# segment as well.
+$backup_label =~
+  /^START WAL LOCATION: [0-9A-F\/]+ \(file ([0-9A-F]{8})[0-9A-F]{16}\)$/m
+  or die "WAL file name missing from backup_label";
+my $shutdown_wal = $1
+  . $node_b->safe_psql('postgres',
+	"SELECT substr(pg_walfile_name('$shutdown_ckpt'), 9);");
+
+command_like(
 	[
 		'pg_waldump',
 		'-p' => $node_a->data_dir . '/pg_wal',
-		'-t' => 1,
 		'-s' => $shutdown_ckpt,
 		'-n' => 1,
-	]);
-like($stdout, qr/CHECKPOINT_SHUTDOWN/,
+		$shutdown_wal,
+	],
+	qr/CHECKPOINT_SHUTDOWN/,
 	'last common checkpoint is a shutdown checkpoint');
 
 # pg_rewind keeps the target's own checksum state in the control file it


[parent: 5f76ed5d6baa]