From: Laurenz Albe <laurenz.albe@cybertec.at>
To: John Scalia <jayknowsunix@gmail.com>
To: Pgsql-admin <pgsql-admin@lists.postgresql.org>
Subject: Re: Disabling indexes on a table
Date: Fri, 19 Feb 2021 10:23:36 +0100
Message-ID: <66028fd5cc301f5726d759e46903f88f8c18217f.camel@cybertec.at> (raw)
In-Reply-To: <8D9636C9-D38E-4857-A542-1469A11A25FF@gmail.com>
References: <8D9636C9-D38E-4857-A542-1469A11A25FF@gmail.com>
On Thu, 2021-02-18 at 11:24 -0500, John Scalia wrote:
> One of my developers asked me about this, and he suggested running the following update:
>
> UPDATE pg_index SET indisready=false
> WHERE indrelid = (select oid from pg_class where release = ‘his_table’);
>
> I told him it’s never a good idea to update anything in a system catalog by hand,
> but that I would reach out here for a better opinion. Am I correct that he
> shouldn’t try this, or is he OK to do this? His table has approximately 8
> different indexes on it, and those really slow down his bulk loads.
> Usually when I have to get involved, I just drop his indexes and rebuild
> them afterwards, and I know that is always safe.
https://www.postgresql.org/docs/current/catalog-pg-index.html says:
indisready bool
If true, the index is currently ready for inserts. False means the
index must be ignored by INSERT/UPDATE operations.
So that would indeed speed up a bulk load, but your indexes would be
unusable afterwards. If you run a second update to "pg_index" to
set "indisready" to TRUE, you would end up with corrupted indexes.
The indexes will be useless and can only be dropped. So you are right
that that is not a good idea.
Yours,
Laurenz Albe
--
Cybertec | https://www.cybertec-postgresql.com
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-admin@postgresql.org
Cc: laurenz.albe@cybertec.at, jayknowsunix@gmail.com, pgsql-admin@lists.postgresql.org
Subject: Re: Disabling indexes on a table
In-Reply-To: <66028fd5cc301f5726d759e46903f88f8c18217f.camel@cybertec.at>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox