Re: Combine Prune and Freeze records emitted by vacuum

On Wed, Mar 20, 2024 at 4:04 PM Peter Geoghegan <pg(at)bowt(dot)ie> wrote:
>
> On Wed, Mar 20, 2024 at 9:15 AM Heikki Linnakangas <hlinnaka(at)iki(dot)fi> wrote:
> > > I made it its own sub-record (xlhp_conflict_horizon) less to help with
> > > alignment (though we can use all the help we can get there) and more to
> > > keep it from getting lost. When you look at heapam_xlog.h, you can see
> > > what a XLOG_HEAP2_PRUNE record will contain starting with the
> > > xl_heap_prune struct and then all the sub-record types.
> >
> > Ok, now that I look at this, I wonder if we're being overly cautious
> > about the WAL size. We probably could just always include the snapshot
> > field, and set it to InvalidTransactionId and waste 4 bytes when it's
> > not needed. For the sake of simplicity. I don't feel strongly either way
> > though, the flag is pretty simple too.
>
> What about the issue of cleanup locks, which aren't needed and aren't
> taken with the current heapam VACUUM record type? Will you preserve
> that aspect of the existing design?

Yep, we have a flag to indicate whether or not a cleanup lock is needed.

- Melanie