From: Tom Lane <tgl@sss.pgh.pa.us>
To: Thomas Munro <thomas.munro@gmail.com>
cc: Alexander Lakhin <exclusion@gmail.com>, pgsql-bugs@lists.postgresql.org
Subject: Re: BUG #17368: Assert failed in GetSafeSnapshot() for SERIALIZABLE
 READ ONLY DEFERRABLE transaction
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Comments: In-reply-to Thomas Munro <thomas.munro@gmail.com>
	message dated "Tue, 07 Mar 2023 14:14:03 +1300"
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Date: Mon, 06 Mar 2023 20:16:37 -0500
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Thomas Munro <thomas.munro@gmail.com> writes:
> On Tue, Mar 7, 2023 at 12:42 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> What if they both touched/modified a shared catalog?

> I was assuming that that would already skip all predicate locking because:

> /*
>  * Does this relation participate in predicate locking? Temporary and system
>  * relations are exempt.
>  */

Oh, I'd forgotten about that.

> If we ever wanted to use SSI on catalogs, or allow shared relations
> that aren't catalogs, or allow cross-database access, then this
> optimisation wouldn't fly.

I suppose there are some gotchas in the way of making that happen,
so okay.

			regards, tom lane