Horton

Re: logical decoding and replication of sequences

Amit Kapila <amit.kapila16@gmail.com>

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From: Amit Kapila <amit.kapila16@gmail.com>
To: Masahiko Sawada <sawada.mshk@gmail.com>
Cc: Tomas Vondra <tomas.vondra@enterprisedb.com>, Petr Jelinek <petr.jelinek@enterprisedb.com>, Peter Eisentraut <peter.eisentraut@enterprisedb.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2022-04-04T11:45:36Z
Lists: pgsql-hackers 
On Mon, Apr 4, 2022 at 11:42 AM Masahiko Sawada <sawada.mshk@gmail.com> wrote:
>
> On Sat, Apr 2, 2022 at 8:52 PM Tomas Vondra
> <tomas.vondra@enterprisedb.com> wrote:
>
> It's not related to this issue but I think that non-transactional
> sequence changes could be resent in case of the subscriber crashes
> because it doesn’t update replication origin LSN, is that right? If
> so, while resending the sequence changes, the sequence value on the
> subscriber can temporarily go backward.
>

Yes, this can happen for the non-transactional sequence changes though
this is a different problem than what is happening on the decoding
side.

> > >> Also, there's the bug with decoding changes in transactions that create
> > >> the sequence and add it to a publication. I think the agreement was that
> > >> this behavior was incorrect, we should not decode changes until the
> > >> subscription is refreshed. Doesn't that mean can't be any CREATE case,
> > >> just ALTER?
> > >>
> > >
> > > Yeah, but how will we distinguish them. Aren't they using the same
> > > kind of WAL record?
> > >
> >
> > Same WAL record, but the "created" flag which should distinguish these
> > two cases, IIRC.
>
> Since the "created" flag indicates that we created a new relfilenode
> so it's true when both CREATE and ALTER.
>

Yes, this is my understanding as well. So, we need something else.

-- 
With Regards,
Amit Kapila.

Commits

  1. Fix cache invalidation bug in recovery_prefetch.

  2. Revert "Logical decoding of sequences"

  3. Minor improvements in sequence decoding code and docs

  4. Handle sequences in preprocess_pubobj_list

  5. Update tab-completion for CREATE PUBLICATION with sequences

  6. Add decoding of sequences to built-in replication

  7. Stabilize test_decoding touching with sequences

  8. Call ReorderBufferProcessXid from sequence_decode

  9. Add decoding of sequences to test_decoding

  10. Replace Test::More plans with done_testing

  11. Logical decoding of sequences

  12. Respect permissions within logical replication.