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In-Reply-To: <20220220030128.sgytb3wccteb3opj@alap3.anarazel.de>
From: Peter Geoghegan <pg@bowt.ie>
Date: Sat, 19 Feb 2022 19:18:25 -0800
Message-ID: <CAH2-WzkUXpAMKpytrRUtPkfQSXznaas3EyEsh7rLUrhsCqzuQw@mail.gmail.com>
Subject: Re: Removing more vacuumlazy.c special cases, relfrozenxid optimizations
To: Andres Freund <andres@anarazel.de>
Cc: Robert Haas <robertmhaas@gmail.com>, Masahiko Sawada <sawada.mshk@gmail.com>, 
	PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
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On Sat, Feb 19, 2022 at 7:01 PM Andres Freund <andres@anarazel.de> wrote:
> It's kind of surprising that this needs this
> 0001-Add-adversarial-ConditionalLockBuff to break. I suspect it's a question
> of hint bits changing due to lazy_scan_noprune(), which then makes
> HeapTupleHeaderIsHotUpdated() have a different return value, preventing the
> "If the tuple is DEAD and doesn't chain to anything else"
> path from being taken.

That makes sense as an explanation. Goes to show just how fragile the
"DEAD and doesn't chain to anything else" logic at the top of
heap_prune_chain really is.

-- 
Peter Geoghegan