Hi, On Fri, Feb 24, 2023 at 7:08 AM Melanie Plageman <melanieplage...@gmail.com> wrote: > > Hi, > > Users may wish to speed up long-running vacuum of a large table by > decreasing autovacuum_vacuum_cost_delay/vacuum_cost_delay, however the > config file is only reloaded between tables (for autovacuum) or after > the statement (for explicit vacuum). This has been brought up for > autovacuum in [1]. > > Andres suggested that it might be possible to check ConfigReloadPending > in vacuum_delay_point(), so I thought I would draft a rough patch and > start a discussion.
In vacuum_delay_point(), we need to update VacuumCostActive too if necessary. > Apart from this, one higher level question I have is if there are other > gucs whose modification would make reloading the configuration file > during vacuum/analyze unsafe. 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. 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. 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(). Regards, -- Masahiko Sawada Amazon Web Services: https://aws.amazon.com
