Re: Logical Replication of sequences

On Sat, Oct 04, 2025 at 09:24:32PM +0530, Amit Kapila wrote:
> In the 0001 patch, pg_get_sequence_data() exposes two new fields
> log_cnt and page_lsn. I see that the later subscriber-side patch uses
> both, the first one in SetSequence(). It is not clear from the
> comments or the commit message of 0001 why it is necessary to use
> log_cnt when setting the sequence. Can you explain what the problem
> will be if we don't use log_cnt during sequence sync?

FWIW, I have argued two times at least that it should never be
necessary to expose log_cnt in the sequence meta-data: this is just a
counter to decide when a WAL record of a sequence should be generated.

If you are copying some sequence data over the wire on a new node in a
logical shape where WAL is independent, this counter is irrelevant:
you can just reset it.  Please see also a83a944e9fdd.
--
Michael