A much more sensible answer is to initialize the segno to the segment currently being written, as in the attached.
-- Álvaro Herrera https://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
>From 699e3a25e0673353fcb10fa92577f7534e594227 Mon Sep 17 00:00:00 2001 From: Alvaro Herrera <alvhe...@alvh.no-ip.org> Date: Mon, 13 Jul 2020 13:22:40 -0400 Subject: [PATCH v3] Fix uninitialized value in segno calculation Remove previous hack in KeepLogSeg that added a case to deal with a (badly represented) invalid segment number; to replace it, initialize the segment number to be retreated to the currently being written segment. Per valgrind-running buildfarm member skink, and some sparc64 animals. Discussion: https://postgr.es/m/1724648.1594230...@sss.pgh.pa.us --- src/backend/access/transam/xlog.c | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-) diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 28daf72a50..0a97b1d37f 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -9523,13 +9523,13 @@ GetWALAvailability(XLogRecPtr targetLSN) if (XLogRecPtrIsInvalid(targetLSN)) return WALAVAIL_INVALID_LSN; - currpos = GetXLogWriteRecPtr(); - /* - * calculate the oldest segment currently reserved by all slots, - * considering wal_keep_segments and max_slot_wal_keep_size + * Calculate the oldest segment currently reserved by all slots, + * considering wal_keep_segments and max_slot_wal_keep_size. Initialize + * oldestSlotSeg to the current segment. */ - XLByteToSeg(targetLSN, targetSeg, wal_segment_size); + currpos = GetXLogWriteRecPtr(); + XLByteToSeg(currpos, oldestSlotSeg, wal_segment_size); KeepLogSeg(currpos, &oldestSlotSeg); /* @@ -9548,6 +9548,9 @@ GetWALAvailability(XLogRecPtr targetLSN) else oldestSegMaxWalSize = 1; + /* the segment we care about */ + XLByteToSeg(targetLSN, targetSeg, wal_segment_size); + /* * No point in returning reserved or extended status values if the * targetSeg is known to be lost. @@ -9624,7 +9627,7 @@ KeepLogSeg(XLogRecPtr recptr, XLogSegNo *logSegNo) } /* don't delete WAL segments newer than the calculated segment */ - if (XLogRecPtrIsInvalid(*logSegNo) || segno < *logSegNo) + if (segno < *logSegNo) *logSegNo = segno; } -- 2.20.1
