From: Tom Lane <tgl@sss.pgh.pa.us>
To: Peter Geoghegan <pg@bowt.ie>
cc: Andres Freund <andres@anarazel.de>,
        PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Subject: Re: PANIC: wrong buffer passed to visibilitymap_clear
In-reply-to: <2691106.1618162892@sss.pgh.pa.us>
References: <2247102.1618008027@sss.pgh.pa.us>
 <20210409232739.sazp5p4xnnagrusa@alap3.anarazel.de>
 <20210409233203.3khg3s5iw34g4xrc@alap3.anarazel.de>
 <2644575.1618117467@sss.pgh.pa.us>
 <CAH2-WzmWOLaWhQgEC1BJN0JZpOCOwxCAhjmd2Nd4yh4wrqju8Q@mail.gmail.com>
 <2679216.1618156670@sss.pgh.pa.us>
 <CAH2-WzmJ7THDU3jPgRH8J++b+pSoOh8nfGZEhNHh+4=LFatDeg@mail.gmail.com>
 <CAH2-WzkCXg6RQJdc_7ZGHcKvyoJAfFu9R2ZVAiE9mCcOfaXJdQ@mail.gmail.com>
 <2689873.1618161194@sss.pgh.pa.us> <2691106.1618162892@sss.pgh.pa.us>
Comments: In-reply-to Tom Lane <tgl@sss.pgh.pa.us>
	message dated "Sun, 11 Apr 2021 13:41:32 -0400"
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-ID: <2691723.1618163729.1@sss.pgh.pa.us>
Date: Sun, 11 Apr 2021 13:55:30 -0400
Message-ID: <2691724.1618163730@sss.pgh.pa.us>
Archived-At: 
 <https://www.postgresql.org/message-id/2691724.1618163730%40sss.pgh.pa.us>
Precedence: bulk

I wrote:
> I'm now inclined to think that we should toss every single line of that
> code, take RelationGetBufferForTuple out of the equation, and have just
> *one* place that rechecks for PageAllVisible having just become set.
> It's a rare enough case that optimizing it is completely not worth the
> code complexity and risk (er, reality) of hard-to-locate bugs.

Alternatively, we could do what you suggested and redefine things
so that one is only allowed to set the all-visible bit while holding
superexclusive lock; which again would allow an enormous simplification
in heap_update and cohorts.  Either way, it's hard to argue that
heap_update hasn't crossed the complexity threshold where it's
impossible to maintain safely.  We need to simplify it.

			regards, tom lane