Re: decoupling table and index vacuum

On Thu, May 6, 2021 at 7:19 PM Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
>
> On Thu, May 6, 2021 at 5:02 AM Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
> > Not sure we will need to hold buffer locks for both the TID fork and
> > the heap at the same time but I agree that we could need to lock on
> > multiple TID fork buffers. We could need to add dead TIDs to up to two
> > pages for the TID fork during replaying XLOG_HEAP2_PRUNE since we
> > write it per heap pages. Probably we can process one by one.
>
> It seems like we do need to hold them at the same time, because
> typically for a WAL record you lock all the buffers, modify them all
> while writing the WAL record, and then unlock them all.
>
> Now maybe there's some argument that we can dodge that requirement
> here, but I have reservations about departing from the usual locking
> pattern. It's easier to reason about the behavior when everybody
> follows the same set of rules.

Yes, agreed. I was thinking of replaying WAL, not writing WAL.

Regards,

--
Masahiko Sawada
EDB: https://www.enterprisedb.com/