Horton

Re: Should vacuum process config file reload more often

Masahiko Sawada <sawada.mshk@gmail.com>

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From: Masahiko Sawada <sawada.mshk@gmail.com>
To: Andres Freund <andres@anarazel.de>
Cc: Melanie Plageman <melanieplageman@gmail.com>, Pg Hackers <pgsql-hackers@postgresql.org>
Date: 2023-02-28T02:16:45Z
Lists: pgsql-hackers 
On Tue, Feb 28, 2023 at 10:21 AM Andres Freund <andres@anarazel.de> wrote:
>
> Hi,
>
> On 2023-02-27 23:11:53 +0900, Masahiko Sawada wrote:
> > As far as I know there are not such GUC parameters in the core but
> > there might be in third-party table AM and index AM extensions.
>
> We already reload in a pretty broad range of situations, so I'm not sure
> there's a lot that could be unsafe that isn't already.
>
>
> > Also, I'm concerned that allowing to change any GUC parameters during
> > vacuum/analyze could be a foot-gun in the future. When modifying
> > vacuum/analyze-related codes, we have to consider the case where any GUC
> > parameters could be changed during vacuum/analyze.
>
> What kind of scenario are you thinking of?

For example, I guess we will need to take care of changes of
maintenance_work_mem. Currently we initialize the dead tuple space at
the beginning of lazy vacuum, but perhaps we would need to
enlarge/shrink it based on the new value?

Regards,

-- 
Masahiko Sawada
Amazon Web Services: https://aws.amazon.com

Commits

  1. Fix assertion failure in heap_vacuum_rel

  2. Fix vacuum_cost_delay check for balance calculation.

  3. Fix autovacuum cost debug logging

  4. Refresh cost-based delay params more frequently in autovacuum

  5. Separate vacuum cost variables from GUCs

  6. Make vacuum failsafe_active globally visible

  7. Don't balance vacuum cost delay when per-table settings are in effect