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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Peter Geoghegan <pg@bowt.ie>
Cc: Hans Buschmann <buschmann@nidsa.net>
Cc: Amit Langote <amitlangote09@gmail.com>
Cc: David G. Johnston <david.g.johnston@gmail.com>
Cc: pgsql-bugs@lists.postgresql.org <pgsql-bugs@lists.postgresql.org>
Subject: Re: AW: AW: BUG #18147: ERROR: invalid perminfoindex 0 in RTE with relid xxxxx
Date: Mon, 23 Oct 2023 21:06:01 -0400
Message-ID: <462249.1698109561@sss.pgh.pa.us> (raw)
In-Reply-To: <CAH2-WzkYBZ8qCsMs8i3BuKFLXO2UGKLiB+hhQZDC7=3Y+yf1pA@mail.gmail.com>
References: <18147-6fc796538913ee88@postgresql.org>
	<CAKFQuwYFq-Q2rxbXXBmdHCAEFm-Pu_qhPAEi-PO+LmjtYN2hhg@mail.gmail.com>
	<2796464.1696525626@sss.pgh.pa.us>
	<9fdfed847859435e8641e613198be9e3@nidsa.net>
	<3319880.1696778678@sss.pgh.pa.us>
	<3c9fe737f6aa4ae9b0dc19bffd97e106@nidsa.net>
	<408285.1698085850@sss.pgh.pa.us>
	<CAH2-WzmY-1GPgLV=3HXPMf0DPwZCjeVVceMSViaoMj=unL1Qtw@mail.gmail.com>
	<411084.1698087308@sss.pgh.pa.us>
	<CAH2-Wzk=D3X3fKPeg-u1VirLOKU64xcjSnqyuStiFw2kYJuuGw@mail.gmail.com>
	<CAH2-WzmU_BQ=-H9L+bxTSMQBqHMjp1DSwGypvL0gKs+dTOfkKg@mail.gmail.com>
	<458056.1698107313@sss.pgh.pa.us>
	<CAH2-WzkYBZ8qCsMs8i3BuKFLXO2UGKLiB+hhQZDC7=3Y+yf1pA@mail.gmail.com>

Peter Geoghegan <pg@bowt.ie> writes:
> On Mon, Oct 23, 2023 at 5:28 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:
>>> Separately, I wonder if index_unchanged_by_update should actually just
>>> always give the hint with a non-HOT update, regardless of the
>>> specifics for each index/its columns -- just like on the v14 branch.

>> I'm confused.  Wouldn't that be the exact opposite of "unchanged"?

> Well, in practice "indexUnchanged = true" means "do bottom-up deletion
> if it's the only way to avoid a page split". The justification is that
> the incoming tuple is "logically unchanged" (actually it's more
> complicated than that, but that's our starting point).

But doesn't the need for a non-HOT update show that the tuple *was*
changed --- in index-relevant columns, even?  Maybe I'm still not
understanding exactly what condition we're detecting.

			regards, tom lane





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  Subject: Re: AW: AW: BUG #18147: ERROR: invalid perminfoindex 0 in RTE with relid xxxxx
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