Re: logical decoding and replication of sequences, take 2

On Wed, Jan 11, 2023 at 3:28 PM Andres Freund <andres(at)anarazel(dot)de> wrote:
> On 2023-01-11 15:23:18 -0500, Robert Haas wrote:
> > Yeah, I meant if #1 had committed and then #2 started to do its thing.
> > I was worried that decoding might reach the nextval operations in
> > transaction #2 before it replayed #1.
> >
> > This worry may be entirely based on me not understanding how this
> > actually works. Do we always apply a transaction as soon as we see the
> > commit record for it, before decoding any further?
>
> Yes.
>
> Otherwise we'd have a really hard time figuring out the correct historical
> snapshot to use for subsequent transactions - they'd have been able to see the
> catalog modifications made by the committing transaction.

I wonder, then, what happens if somebody wants to do parallel apply.
That would seem to require some relaxation of this rule, but then
doesn't that break what this patch wants to do?

--
Robert Haas
EDB: http://www.enterprisedb.com