Re: Parallel heap vacuum

On Wed, Mar 12, 2025 at 3:17 AM Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
>
> On Tue, Mar 11, 2025 at 5:51 AM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> >

Some thoughts/questions on the idea

I notice that we are always considering block-level parallelism for
heaps and object-level parallelism for indexes. I'm wondering, when
multiple tables are being vacuumed together—either because the user
has provided a list of tables or has specified a partitioned table
with multiple children—does it still make sense to default to
block-level parallelism? Or could we consider table-level parallelism
in such cases? For example, if there are 4 tables and 6 workers, with
2 tables being small and the other 2 being large, perhaps we could
allocate 4 workers to vacuum all 4 tables in parallel. For the larger
tables, we could apply block-level parallelism, using more workers for
internal parallelism. On the other hand, if all tables are small, we
could just apply table-level parallelism without needing block-level
parallelism at all. This approach could offer more flexibility, isn't
it?

--
Regards,
Dilip Kumar
EnterpriseDB: http://www.enterprisedb.com