Feedback-ID: id4a34324:Fastmail
Date: Fri, 13 Mar 2026 11:55:53 -0400
From: Andres Freund <andres@anarazel.de>
To: Alexander Lakhin <exclusion@gmail.com>,
	Alexander Kuzmenkov <akuzmenkov@tigerdata.com>
Cc: Noah Misch <noah@leadboat.com>, Heikki Linnakangas <hlinnaka@iki.fi>,
	Melanie Plageman <melanieplageman@gmail.com>,
 Kirill Reshke <reshkekirill@gmail.com>,
	Matthias van de Meent <boekewurm+postgres@gmail.com>,
 pgsql-hackers@postgresql.org,
	Thomas Munro <thomas.munro@gmail.com>, Robert Haas <robertmhaas@gmail.com>,
	Michael Paquier <michael.paquier@gmail.com>
Subject: Re: Buffer locking is special (hints, checksums, AIO writes)
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Hi,

On 2026-03-13 10:00:00 +0200, Alexander Lakhin wrote:
> Hello Andres,
> 
> 12.03.2026 00:40, Andres Freund wrote:
> > I pushed this and many of the later patches in the series.  Here are updated
> > versions of the remaining changes.  The last two previously were one commit
> > with "WIP" in the title. The first one has, I think, not had a lot of review -
> > but it's also not a complicated change.
> 
> I've discovered that starting from 82467f627, the following query:
> SET cpu_operator_cost = 1000;
> CREATE TABLE t (i INT);
> INSERT INTO T SELECT 1 FROM generate_series(1, 1000) a;
> CREATE INDEX hi on t USING HASH (i);
> DELETE FROM t WHERE i = 1;
> DELETE FROM t WHERE i = 1;
> 
> triggers
> TRAP: failed Assert("BufferIsValid(buffer)"), File: "bufmgr.c", Line: 497, PID: 3942058
> 
> #4  0x000079a60ae288ff in __GI_abort () at ./stdlib/abort.c:79
> #5  0x00005a68d9343eef in ExceptionalCondition (conditionName=conditionName@entry=0x5a68d93ac27d "BufferIsValid(buffer)",
>     fileName=fileName@entry=0x5a68d93c99ef "bufmgr.c", lineNumber=lineNumber@entry=497) at assert.c:65
> #6  0x00005a68d91a18eb in GetPrivateRefCountEntry (do_move=true, buffer=<optimized out>) at bufmgr.c:497
> #7  SharedBufferBeginSetHintBits (lockstate=<synthetic pointer>, buf_hdr=0x79e5febbbc40, buffer=<optimized out>)
>     at bufmgr.c:6830
> #8  BufferBeginSetHintBits (buffer=<optimized out>) at bufmgr.c:6931
> #9  0x00005a68d8e3c862 in _hash_kill_items (scan=<optimized out>) at hashutil.c:603
> #10 0x00005a68d8e3b7c3 in _hash_next (scan=0x5a68e735f938, dir=<optimized out>) at hashsearch.c:69
> #11 0x00005a68d8e616ce in index_getnext_tid (scan=scan@entry=0x5a68e735f938, direction=direction@entry=ForwardScanDirection)
>     at indexam.c:647
> ...
> #25 0x00005a68d91eb4ad in exec_simple_query (query_string=0x5a68e7270120 "DELETE FROM t WHERE i = 1;") at postgres.c:1277
> ...
> 
> Could you please look at this?

Yea, it's a stupid small mistake. Alexander Kuzmenkov reported it late
afternoon yesterday, privately as I just noticed, and I was too tired to make
sure an added test wouldn't have stability issues.

Will fix in the next few hours.

Greetings,

Andres Freund