Re: Vacuuming the free space map considered harmful?

On Wed, Mar 19, 2025 at 4:54 AM Christophe Pettus <xof(at)thebuild(dot)com> wrote:
>
> Everything seems to point to the vacuum free space map operation, since it would have a lot of work to do in that particular situation, it happens at just the right place in the vacuum cycle, and its resource consumption is not throttled the way the regular vacuum operation is.

Do you know how big the FSM was?

As others have said, it could be worth adding a phase to
pg_stat_progress_vacuum.

I know you said you saw this all the way back to 15, but it made me
wonder if this would actually get worse after 17 and the tidstore
optimization -- since a large table with indexes requiring multiple
vacuum passes would actually end up having its FSM vacuumed sooner.

- Melanie