Re: How to run in parallel in Postgres, EXECUTE_PARALLEL

From: Lars Aksel Opsahl <Lars(dot)Opsahl(at)nibio(dot)no>
To: Laurenz Albe <laurenz(dot)albe(at)cybertec(dot)at>, "pgsql-performance(at)lists(dot)postgresql(dot)org" <pgsql-performance(at)lists(dot)postgresql(dot)org>
Subject: Re: How to run in parallel in Postgres, EXECUTE_PARALLEL
Date: 2019-12-08 18:14:14
Message-ID: HE1P189MB0266588071668BF3D5CF85479D590@HE1P189MB0266.EURP189.PROD.OUTLOOK.COM
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>You cannot run several queries in parallel in a PostgreSQL function.
>
>You may want to have a look at PL/Proxy which might be used for things like that.
>
>Yours,
>Laurenz Albe
>--
>Cybertec | https://www.cybertec-postgresql.com

Hi Laurenz

The code below takes 3, seconds
DO

$body$

DECLARE

BEGIN

EXECUTE 'SELECT pg_sleep(1); SELECT pg_sleep(1); SELECT pg_sleep(1);';

END

$body$;

Do you or anybody know if there are any plans for a function call that support the calling structure below or something like it and that then could finish in 1 second ? (If you are calling a void function, the return value should not be any problem.)

DO

$body$

DECLARE

command_string_list text[3];

BEGIN

command_string_list[0] = 'SELECT pg_sleep(1)';

command_string_list[1] = 'SELECT pg_sleep(1)';

command_string_list[2] = 'SELECT pg_sleep(1)';

EXECUTE_PARALLEL command_string_list;

END

$body$;

The only way to this today as I understand it, is to open 3 new connections back to the database which you can be done in different ways.

If we had a parallel functions like the one above it's easier to make parallel sql without using complex scripts, java, python or other system.

Thanks.

Lars

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