From 463e8616f4274be54f680597c26f054811396699 Mon Sep 17 00:00:00 2001 From: Kyotaro Horiguchi Date: Thu, 20 Apr 2023 11:51:10 +0900 Subject: [PATCH v2] Fix incorrect calculation regarding max_slot_wal_keep_size The calculation in KeepLogSeg related to max_slot_wal_keep_size can result in unexpected behavior when replication advances quickly, and the checkpointer is delayed just before removing WAL files. --- src/backend/access/transam/xlog.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 63481d826f..bda859c299 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7463,6 +7463,14 @@ KeepLogSeg(XLogRecPtr recptr, XLogSegNo *logSegNo) { XLByteToSeg(keep, segno, wal_segment_size); + /* + * Slot minimum LSN could be greater than recptr. In such cases, no + * segments are protected by slots but we still need to keep segno in a + * reasonable range for subsequent calculations to avoid underflow. + */ + if (segno > currSegNo) + segno = currSegNo; + /* Cap by max_slot_wal_keep_size ... */ if (max_slot_wal_keep_size_mb >= 0) { -- 2.31.1