From: Tom Lane <tgl@sss.pgh.pa.us>
To: Pavel Stehule <pavel.stehule@gmail.com>
cc: pgsql-hackers@lists.postgresql.org
Subject: Re: Modernizing our GUC infrastructure
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Comments: In-reply-to Pavel Stehule <pavel.stehule@gmail.com>
	message dated "Tue, 06 Sep 2022 06:35:56 +0200"
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Date: Tue, 06 Sep 2022 01:42:53 -0400
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Pavel Stehule <pavel.stehule@gmail.com> writes:
> út 6. 9. 2022 v 6:32 odesílatel Pavel Stehule <pavel.stehule@gmail.com>
> napsal:
>> 1. Session variables can be persistent - so the usage of session variables
>> can be checked by static analyze like plpgsql_check

> more precious - metadata of session variables are persistent

Right ... so the question is, is that a feature or a bug?

I think there's a good analogy here to temporary tables.  The SQL
spec says that temp-table schemas are persistent and database-wide,
but what we actually have is that they are session-local.  People
occasionally propose that we implement the SQL semantics for that,
but in the last twenty-plus years no one has bothered to write a
committable patch to support it ... much less remove the existing
behavior in favor of that, which I'm pretty sure no one would think
is a good idea.

So, is it actually a good idea to have persistent metadata for
session variables?  I'd say that the issue is at best debatable,
and at worst proven wrong by a couple of decades of experience.
In what way are session variables less mutable than temp tables?

Still, this discussion would be better placed on the other thread.

			regards, tom lane