From: Jonathan S. Katz <jkatz@postgresql.org>
To: Andres Freund <andres@anarazel.de>
Cc: Andrew Dunstan <andrew@dunslane.net>
Cc: Amit Langote <amitlangote09@gmail.com>
Cc: David Rowley <dgrowleyml@gmail.com>
Cc: Alvaro Herrera <alvherre@alvh.no-ip.org>
Cc: Michael Paquier <michael@paquier.xyz>
Cc: John Naylor <john.naylor@enterprisedb.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Peter Geoghegan <pg@bowt.ie>
Cc: PostgreSQL-development <pgsql-hackers@postgresql.org>
Cc: Nikita Glukhov <n.gluhov@postgrespro.ru>
Subject: Re: PG 15 (and to a smaller degree 14) regression due to ExprEvalStep size
Date: Tue, 9 Aug 2022 15:59:44 -0400
Message-ID: <5010c184-088d-f98b-18ea-40ee63be6b04@postgresql.org> (raw)
In-Reply-To: <20220809185725.t477tp54v3qv4uyi@awork3.anarazel.de>
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On 8/9/22 2:57 PM, Andres Freund wrote:
> Hi,
>
> On 2022-08-09 14:04:48 -0400, Jonathan S. Katz wrote:
>>>> 2. Recommend holding up the v15 release to allow for the code to be
>>>> redesigned and fixed (as based on Andres' estimates, this would push
>>>> the release out several months).
>
> Obviously that's a question of the resources brought to bear.
>
> From my angle: I've obviously some of my own work to take care of as well, but
> it's also just hard to improve something that includes a lot of undocumented
> design decisions.
*nod*
>>>> 4. Revert the feature set and redesign and try to include for v16
> Unless we decide on 4 immediately, I think it might be worth starting a
> separate thread to get more attention. The subject doesn't necessarily have
> everyone follow along.
*nod* I'll do this shortly.
>> Rereading the thread for the umpteenth time, I have seen Amit working
>> through Andres' concerns. From my read, the ones that seem pressing are:
>>
>> * Lack of design documentation, which may be leading to some of the general
>> design concerns
>
>> * The use of substransactions within the executor, though docs explaining
>> the decisions on that could alleviate it (I realize this is a big topic and
>> any summary I give won't capture the full nuance)
>
> I don't think subtransactions per-se are a fundamental problem. I think the
> error handling implementation is ridiculously complicated, and while I started
> to hack on improving it, I stopped when I really couldn't understand what
> errors it actually needs to handle when and why.
Ah, thanks for the clarification. That makes sense.
>> * Debate on how to handle the type coercions
>
> That's partially related to the error handling issue above.
>
> One way this code could be drastically simplified is to force all
> type-coercions to go through the "io coercion" path, which could be
> implemented as a single execution step (which thus could trivially
> start/finish a subtransaction) and would remove a lot of the complicated code
> around coercions.
If we went down this path, would this make you feel more comfortable
with including this work in the v15 release?
Thanks,
Jonathan
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To: pgsql-hackers@postgresql.org
Cc: jkatz@postgresql.org, andres@anarazel.de, andrew@dunslane.net, amitlangote09@gmail.com, dgrowleyml@gmail.com, alvherre@alvh.no-ip.org, michael@paquier.xyz, john.naylor@enterprisedb.com, tgl@sss.pgh.pa.us, pg@bowt.ie, n.gluhov@postgrespro.ru
Subject: Re: PG 15 (and to a smaller degree 14) regression due to ExprEvalStep size
In-Reply-To: <5010c184-088d-f98b-18ea-40ee63be6b04@postgresql.org>
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