Re: logical decoding and replication of sequences

On 14.12.21 02:31, Tomas Vondra wrote:
> There's still one remaining problem, that I already explained in [1].
> The problem is that with this:
> 
>    BEGIN;
>    SELECT nextval('s') FROM generate_series(1,100);
>    ROLLBACK;
> 
> 
> The root cause is that pg_current_wal_lsn() uses the LogwrtResult.Write,
> which is updated by XLogFlush() - but only in RecordTransactionCommit.
> Which makes sense, because only the committed stuff is "visible".
> 
> But the non-transactional behavior of sequence decoding disagrees with
> this, because now some of the changes from aborted transactions may be
> replicated. Which means the wait_for_catchup() ends up not waiting for
> the sequence change to be replicated.

I can't think of a reason why this might be a problem.