Horton

Re: Should vacuum process config file reload more often

Andres Freund <andres@anarazel.de>

View thread View on postgr.es
From: Andres Freund <andres@anarazel.de>
To: Masahiko Sawada <sawada.mshk@gmail.com>
Cc: Melanie Plageman <melanieplageman@gmail.com>, Pg Hackers <pgsql-hackers@postgresql.org>
Date: 2023-03-02T00:15:35Z
Lists: pgsql-hackers 
Hi,

On 2023-02-28 11:16:45 +0900, Masahiko Sawada wrote:
> On Tue, Feb 28, 2023 at 10:21 AM Andres Freund <andres@anarazel.de> wrote:
> > 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?

I don't think we need to do anything about that initially, just because the
config can be changed in a more granular way, doesn't mean we have to react to
every change for the current operation.

Greetings,

Andres Freund

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