Re: maintenance_work_mem = 64kB doesn't work for vacuum

On Mon, 10 Mar 2025 at 07:46, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
> A simple fix is to bump the minimum maintenance_work_mem to 256kB. We
> would break the compatibility for backbranch (i.e. v17) but I guess
> it's unlikely that existing v17 users are using less than 1MB
> maintenance_work_mem (the release note doesn't mention the fact that
> we lowered the minimum value).

Could you do something similar to what's in hash_agg_check_limits()
where we check we've got at least 1 item before bailing before we've
used up the all the prescribed memory? That seems like a safer coding
practise as if in the future the minimum usage for a DSM segment goes
above 256KB, the bug comes back again.

David