Re: Logical Replication of sequences

On Mon, 10 Jun 2024 at 12:24, Amul Sul <sulamul(at)gmail(dot)com> wrote:
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>
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> On Sat, Jun 8, 2024 at 6:43 PM vignesh C <vignesh21(at)gmail(dot)com> wrote:
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>> On Wed, 5 Jun 2024 at 14:11, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>> [...]
>> A new catalog table, pg_subscription_seq, has been introduced for
>> mapping subscriptions to sequences. Additionally, the sequence LSN
>> (Log Sequence Number) is stored, facilitating determination of
>> sequence changes occurring before or after the returned sequence
>> state.
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> Can't it be done using pg_depend? It seems a bit excessive unless I'm missing
> something.

We'll require the lsn because the sequence LSN informs the user that
it has been synchronized up to the LSN in pg_subscription_seq. Since
we are not supporting incremental sync, the user will be able to
identify if he should run refresh sequences or not by checking the lsn
of the pg_subscription_seq and the lsn of the sequence(using
pg_sequence_state added) in the publisher. Also, this parallels our
implementation for pg_subscription_seq and will aid in expanding for
a) incremental synchronization and b) utilizing workers for
synchronization using sequence states if necessary.

How do you track sequence mapping with the publication?

In the publisher we use pg_publication_rel and
pg_publication_namespace for mapping the sequences with the
publication.

Regards,
Vignesh
Vignesh