Re: New GUC autovacuum_max_threshold ?
Sami Imseih <samimseih@gmail.com>
From: Sami Imseih <samimseih@gmail.com>
To: Nathan Bossart <nathandbossart@gmail.com>, Frédéric Yhuel <frederic.yhuel@dalibo.com>
Cc: Robert Treat <rob@xzilla.net>, wenhui qiu <qiuwenhuifx@gmail.com>, Robert Haas <robertmhaas@gmail.com>, "Imseih (AWS),
Sami" <simseih@amazon.com>, David Rowley <dgrowleyml@gmail.com>, Joe Conway <mail@joeconway.com>, Michael Banck <mbanck@gmx.net>, Laurenz Albe <laurenz.albe@cybertec.at>, Melanie Plageman <melanieplageman@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2025-01-14T17:08:36Z
Lists: pgsql-hackers
> Good call. Here is an updated patch. thanks for the update! After staring at the documentation for a while, I am now wondering whether we are adequately describing the rationale for this GUC. The GUC documentation mentions that this is a 'cap on the value calculated with autovacuum_vacuum_threshold and autovacuum_vacuum_scale_factor,' which is acceptable; however, I think further elaboration is necessary in routine-vacuuming.html#AUTOVACUUM. This is because scale_factor and threshold are already well-known and widely understood parameters, and introducing a third one to the mix deserves a bit more of an explanation. What do you think? Based on my understanding of the discussion, the purpose of the GUC is to prevent large tables from experiencing extended periods without an autovacuum, particularly because scale_factor triggers vacuuming less frequently as the table grows. Currently, users can handle such cases by disabling (or lowering) autovacuum_vacuum_scale_factor and setting an appropriate autovacuum_vacuum_threshold; Therefore, this GUC becomes a more convenient and predictable way to ensure autovacuum triggers on a large table. Is this correct? Regards, Sami
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API reference →
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Introduce autovacuum_vacuum_max_threshold.
- 306dc520b9df 18.0 landed
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Consolidate docs for vacuum-related GUCs in new subsection
- ca9c6a5680d7 18.0 cited