Re: Parallel heap vacuum

On Fri, Jan 17, 2025 at 10:43 PM Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com>
wrote:

> On Fri, Jan 17, 2025 at 1:43 AM Dilip Kumar <dilipbalaut(at)gmail(dot)com> wrote:
> >
> > On Fri, Jan 17, 2025 at 6:37 AM Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com>
> wrote:
> >>
> >> On Sun, Jan 12, 2025 at 1:34 AM Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com>
> wrote:
> >> >
> >
> >
> > IIRC, there was one of the blocker for implementing parallel heap vacuum
> was group locking, have we already resolved that issue or its being
> included in this patch set?
>
> I recall we had some discussion on changes to group locking for
> implementing parallel heap vacuum, but I don't remember if we have a
> blocker now.
>

> One problem we previously had was that since the relation extension
> locks were not in conflict between parallel workers and the leader,
> multiple workers could extend the visibility map simultaneously. This
> problem was fixed by commit 85f6b49c2c.
>

Yes, that's correct. As part of that commit, we made the relation extension
lock conflict among group members, ensuring that multiple workers cannot
acquire it simultaneously. Additionally, this cannot cause a deadlock
because no other locks are held while the relation extension lock is being
held.

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