From: Nathan Bossart <nathandbossart@gmail.com>
To: David Rowley <dgrowleyml@gmail.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>
Cc: andrewbille@gmail.com
Cc: pgsql-bugs@lists.postgresql.org
Subject: Re: BUG #19086: pg_dump --data-only selects and do not uses index definitions for the dumped tables.
Date: Wed, 15 Oct 2025 11:24:34 -0500
Message-ID: <aO_KwnHm2AVn0E4m@nathan> (raw)
In-Reply-To: <CAApHDvoU2O-_zKNL-toHwkDcMXCzzvgRUTnA3baEEhCB4vqMRw@mail.gmail.com>
References: <19086-871ff11017d03dc5@postgresql.org>
<aO6mUj9H2WpEFylG@nathan>
<1000041.1760471415@sss.pgh.pa.us>
<aO7IoIEnQDbtFzrs@nathan>
<CAApHDvoU2O-_zKNL-toHwkDcMXCzzvgRUTnA3baEEhCB4vqMRw@mail.gmail.com>
On Wed, Oct 15, 2025 at 12:56:25PM +1300, David Rowley wrote:
> I tried rewriting the query so that pg_attribute is joined to rather
> than subqueries. With 1500 tables I get:
>
> master:
>
> ignore_system_indexes = on
> Execution Time: 6853.262 ms
>
> ignore_system_indexes = off
> Execution Time: 66.781 ms
>
> Rewritten query:
>
> ignore_system_indexes = on
> Execution Time: 53.351 ms
>
> ignore_system_indexes = off
> Execution Time: 56.965 ms
I tried this with 100K tables and saw the following (ignore_system_indexes
= off):
master:
Planning Time: 1.672 ms
Execution Time: 4077.008 ms
rewritten:
Planning Time: 1.641 ms
Execution Time: 3427.206 ms
I tried this with ignore_system_indexes = on, too, but it was very slow.
--
nathan
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To: pgsql-bugs@postgresql.org
Cc: nathandbossart@gmail.com, dgrowleyml@gmail.com, tgl@sss.pgh.pa.us, andrewbille@gmail.com, pgsql-bugs@lists.postgresql.org
Subject: Re: BUG #19086: pg_dump --data-only selects and do not uses index definitions for the dumped tables.
In-Reply-To: <aO_KwnHm2AVn0E4m@nathan>
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