Re: Problem with accessing TOAST data in stored procedures

pá 19. 2. 2021 v 8:39 odesílatel Konstantin Knizhnik <
k(dot)knizhnik(at)postgrespro(dot)ru> napsal:

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> On 19.02.2021 10:14, Pavel Stehule wrote:
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>
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> pá 19. 2. 2021 v 7:51 odesílatel Konstantin Knizhnik <
> k(dot)knizhnik(at)postgrespro(dot)ru> napsal:
>
>>
>>
>> On 18.02.2021 20:10, Pavel Stehule wrote:
>>
>> This has a negative impact on performance - and a lot of users use
>> procedures without transaction control. So it doesn't look like a good
>> solution.
>>
>> I am more concentrated on the Pg 14 release, where the work with SPI is
>> redesigned, and I hope so this issue is fixed there. For older releases, I
>> don't know. Is this issue related to Postgres or it is related to PgPro
>> only? If it is related to community pg, then we should fix and we should
>> accept not too good performance, because there is no better non invasive
>> solution. If it is PgPro issue (because there are ATX support) you can fix
>> it (or you can try backport the patch
>> https://git.postgresql.org/gitweb/?p=postgresql.git;a=commitdiff;h=ee895a655ce4341546facd6f23e3e8f2931b96bf
>> ). You have more possibilities on PgPro code base.
>>
>>
>> Sorry, it is not PgPro specific problem and recent master suffers from
>> this bug as well.
>> In the original bug report there was simple scenario of reproducing the
>> problem:
>>
>> CREATE TABLE toasted(id serial primary key, data text);
>> INSERT INTO toasted(data) VALUES((SELECT string_agg(random()::text,':')
>> FROM generate_series(1, 1000)));
>> INSERT INTO toasted(data) VALUES((SELECT string_agg(random()::text,':')
>> FROM generate_series(1, 1000)));
>> DO $$ DECLARE v_r record; BEGIN FOR v_r in SELECT data FROM toasted LOOP
>> INSERT INTO toasted(data) VALUES(v_r.data);COMMIT;END LOOP;END;$$;
>>
>
> can you use new procedure_resowner?
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> Sorry, I do not understanf your suggestion.
> How procedure_resowner can help to solve this problem?
>

This is just an idea - I think the most correct with zero performance
impact is keeping snapshot, and this can be stored in procedure_resowner.

The fundamental question is if we want or allow more snapshots per query.
The implementation is a secondary issue.

Pavel

>
> --
> Konstantin Knizhnik
> Postgres Professional: http://www.postgrespro.com
> The Russian Postgres Company
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>