Horton

Re: Should vacuum process config file reload more often

Andres Freund <andres@anarazel.de>

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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: 2023-02-28T01:21:37Z
Lists: pgsql-hackers 
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?


> I guess it would be better to apply the parameter changes for only vacuum
> delay related parameters. For example, autovacuum launcher advertises the
> values of the vacuum delay parameters on the shared memory not only for
> autovacuum processes but also for manual vacuum/analyze processes.  Both
> processes can update them accordingly in vacuum_delay_point().

I don't think this is a good idea. It'd introduce a fair amount of complexity
without, as far as I can tell, a benefit.

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