From 390725f4d967bbf37c884c9cfb3c375cb7071fd6 Mon Sep 17 00:00:00 2001
From: alterego655 <824662526@qq.com>
Date: Wed, 27 May 2026 18:50:51 +0800
Subject: [PATCH] Fix safe_wal_size for slots without restart_lsn

pg_replication_slots could report a non-NULL safe_wal_size for a
replication slot that had never reserved WAL, when max_slot_wal_keep_size
was finite. Such a slot has no restart_lsn, so WAL availability and
safe_wal_size are undefined.

Return NULL for safe_wal_size when WAL availability is invalid.
---
 src/backend/replication/slotfuncs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/backend/replication/slotfuncs.c b/src/backend/replication/slotfuncs.c
index 16fbd383735..7d238becd49 100644
--- a/src/backend/replication/slotfuncs.c
+++ b/src/backend/replication/slotfuncs.c
@@ -400,7 +400,7 @@ pg_get_replication_slots(PG_FUNCTION_ARGS)
 		 * safe_wal_size is only computed for slots that have not been lost,
 		 * and only if there's a configured maximum size.
 		 */
-		if (walstate == WALAVAIL_REMOVED || max_slot_wal_keep_size_mb < 0)
+		if (walstate == WALAVAIL_REMOVED || walstate == WALAVAIL_INVALID_LSN || max_slot_wal_keep_size_mb < 0)
 			nulls[i++] = true;
 		else
 		{
-- 
2.51.0