From: | Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> |
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To: | Dmitry Dolgov <9erthalion6(at)gmail(dot)com> |
Cc: | Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>, Peter Eisentraut <peter(dot)eisentraut(at)enterprisedb(dot)com>, Sergey Shinderuk <s(dot)shinderuk(at)postgrespro(dot)ru>, Tomas Vondra <tomas(dot)vondra(at)enterprisedb(dot)com>, Julien Rouhaud <rjuju123(at)gmail(dot)com>, dean(dot)a(dot)rasheed(at)gmail(dot)com, er(at)xs4all(dot)nl, joel(at)compiler(dot)org, pgsql-hackers(at)lists(dot)postgresql(dot)org |
Subject: | Re: Schema variables - new implementation for Postgres 15 |
Date: | 2024-05-18 11:29:09 |
Message-ID: | 202405181129.dayreglflkq6@alvherre.pgsql |
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On 2024-Jan-30, Dmitry Dolgov wrote:
> Yep, in this constellation the implementation holds much better (in
> terms of memory) in my create/let/drop testing.
>
> I've marked the CF item as ready for committer, but a note for anyone
> who would like to pick up it from here -- we're talking about first 5
> patches here, up to the memory cleaning after DROP VARIABLE. It doesn't
> mean the rest is somehow not worth it, but I believe it's a good first
> step.
Hmm, I think patch 16 is essential, because the point of variable shadowing
is a critical aspect of how the whole thing works. So I would say that
a first step would be those first five patches plus 16.
I want to note that when we discussed this patch series at the dev
meeting in FOSDEM, a sort-of conclusion was reached that we didn't want
schema variables at all because of the fact that creating a variable
would potentially change the meaning of queries by shadowing table
columns. But this turns out to be incorrect: it's _variables_ that are
shadowed by table columns, not the other way around.
--
Álvaro Herrera PostgreSQL Developer — https://www.EnterpriseDB.com/
"No hay ausente sin culpa ni presente sin disculpa" (Prov. francés)
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