From: Nathan Bossart <nathandbossart@gmail.com>
To: David G. Johnston <david.g.johnston@gmail.com>
Cc: Fujii Masao <masao.fujii@oss.nttdata.com>
Cc: Robert Treat <rob@xzilla.net>
Cc: Laurenz Albe <laurenz.albe@cybertec.at>
Cc: Gurjeet Singh <gurjeet@singh.im>
Cc: Andres Freund <andres@anarazel.de>
Cc: Will Storey <will@summercat.com>
Cc: Robert Haas <robertmhaas@gmail.com>
Cc: Postgres Hackers <pgsql-hackers@postgresql.org>
Subject: Re: Disabling vacuum truncate for autovacuum
Date: Thu, 20 Mar 2025 13:13:02 -0500
Message-ID: <Z9xaroJSrS44HyKG@nathan> (raw)
In-Reply-To: <CAKFQuwYKtEUYKS+18gRs-xPhn0qOJgM2KGyyWVCODHuVn9F-XQ@mail.gmail.com>
References: <CABwTF4WFp-oNSm6utik6g-1HZBxijTJBcuX7BKD8MYqza+KMnw@mail.gmail.com>
<6f2f2167f4be09e6ca9251c8f69dfe01809d68be.camel@cybertec.at>
<CABV9wwNagobmRMCxs0dKqWmKXaQTUQj+oOOTw=fsPAgbBfVhew@mail.gmail.com>
<Z9g8a4HGLUcSo96v@nathan>
<Z9ohFZtDaZnkch7u@nathan>
<88e3b55a-8ef8-4b53-8d71-6bfde1a07bc1@oss.nttdata.com>
<Z9rlb0jgNLm8ULAB@nathan>
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<CAKFQuwYKtEUYKS+18gRs-xPhn0qOJgM2KGyyWVCODHuVn9F-XQ@mail.gmail.com>
On Thu, Mar 20, 2025 at 09:59:45AM -0700, David G. Johnston wrote:
> I get the need for this kind of logic, since we used a boolean for the
> table option, but as a self-proclaimed hack it seems worth more comments
> than provided here. Especially pertaining to whether this is indeed
> generic or vacuum_truncate specific. It's unclear since both isset and
> vacuum_truncate_set have been introduced.
I'm happy to expand the comments, but...
> If it is now a general property
> applying to any setting then vacuum_truncate_set shouldn't be needed - we
> should just get the isset value of the existing vacuum_truncate reloption
> by name.
the reason I added this field is because I couldn't find any existing way
to get this information where it's needed. So, I followed the existing
pattern of adding an offset to something we can access. This can be used
for any reloption, but currently vacuum_truncate is the only one that does.
How does something like this look for the comment?
/*
* isset_offset is an optional offset of a field in the result struct
* that stores whether the value is explicitly set for the relation or
* has just picked up the default value. In most cases, this can be
* deduced by giving the reloption a special default value (e.g., -2 is
* a common one for integer reloptions), but this isn't always
* possible. One notable example is Boolean reloptions, where it's
* difficult to discern the source of the value. This offset is only
* used if given a value greater than zero.
*/
int isset_offset;
--
nathan
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To: pgsql-general@postgresql.org
Cc: nathandbossart@gmail.com, david.g.johnston@gmail.com, masao.fujii@oss.nttdata.com, rob@xzilla.net, laurenz.albe@cybertec.at, gurjeet@singh.im, andres@anarazel.de, will@summercat.com, robertmhaas@gmail.com, pgsql-hackers@postgresql.org
Subject: Re: Disabling vacuum truncate for autovacuum
In-Reply-To: <Z9xaroJSrS44HyKG@nathan>
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