Re: Computing the conflict xid for index page-level-vacuum on primary

Hi,

On 2018-12-14 21:39:48 +0300, Alexander Korotkov wrote:
> On Fri, Dec 14, 2018 at 4:43 AM Andres Freund <andres(at)anarazel(dot)de> wrote:
> > This leads me to think that we possibly should move computation of the
> > last removed xid from recovery to the primary, during the generation of
> > the xl_btree_delete WAL record.
>
> Do I understand correctly that we need this xid computation, because
> we may delete some index tuples using kill_prior_tuple before we prune
> corresponding heap tuples (which would be also replicated and cause
> required conflict)?

Correct.

> If so, then can we just give up with that? That is before setting
> kill_prior_tuple = true, prune corresponding heap tuples.

That'd require WAL logging such changes, which'd be pretty bad, because
we'd need to do it one-by-one. What we could do, and what I suggested
earlier, is that we do a bit more pruning when emitting such WAL
records.

Greetings,

Andres Freund