Date: Fri, 10 Jul 2020 19:40:37 -0400
From: Alvaro Herrera <alvherre@2ndquadrant.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: pgbf@twiska.com, Kyotaro Horiguchi <horikyota.ntt@gmail.com>,
	masao.fujii@oss.nttdata.com, pgsql-hackers@lists.postgresql.org
Subject: Re: min_safe_lsn column in pg_replication_slots view
Message-ID: <20200710234037.GA24580@alvherre.pgsql>
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On 2020-Jul-09, Alvaro Herrera wrote:

> I think we should define InvalidXLogSegNo to be ~((uint64)0) and add a
> macro to test for that.

That's overkill really.  I just used zero.  Running
contrib/test_decoding under valgrind, this now passes.

I think I'd rather do away with the compare to zero, and initialize to
something else in GetWALAvailability, though.  What we're doing seems
unclean and unclear.

-- 
Álvaro Herrera                https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

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From 07546b71190b27433e673ff7d248e0f98215abb1 Mon Sep 17 00:00:00 2001
From: Alvaro Herrera <alvherre@alvh.no-ip.org>
Date: Fri, 10 Jul 2020 11:27:55 -0400
Subject: [PATCH] fix uninitialized value

---
 src/backend/access/transam/xlog.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 28daf72a50..3d828cc56f 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -9530,6 +9530,7 @@ GetWALAvailability(XLogRecPtr targetLSN)
 	 * considering wal_keep_segments and max_slot_wal_keep_size
 	 */
 	XLByteToSeg(targetLSN, targetSeg, wal_segment_size);
+	oldestSlotSeg = 0;
 	KeepLogSeg(currpos, &oldestSlotSeg);
 
 	/*
@@ -9624,7 +9625,7 @@ KeepLogSeg(XLogRecPtr recptr, XLogSegNo *logSegNo)
 	}
 
 	/* don't delete WAL segments newer than the calculated segment */
-	if (XLogRecPtrIsInvalid(*logSegNo) || segno < *logSegNo)
+	if (*logSegNo == 0 || segno < *logSegNo)
 		*logSegNo = segno;
 }
 
-- 
2.20.1


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