Re: Logical Replication of sequences

Hi,

On Tue, Jun 4, 2024 at 4:27 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>
> 3. Replicate published sequences via walsender at the time of shutdown
> or incrementally while decoding checkpoint record. The two ways to
> achieve this are: (a) WAL log a special NOOP record just before
> shutting down checkpointer. Then allow the WALsender to read the
> sequence data and send it to the subscriber while decoding the new
> NOOP record. (b) Similar to the previous idea but instead of WAL
> logging a new record directly invokes a decoding callback after
> walsender receives a request to shutdown which will allow pgoutput to
> read and send required sequences. This approach has a drawback that we
> are adding more work at the time of shutdown but note that we already
> waits for all the WAL records to be decoded and sent before shutting
> down the walsender during shutdown of the node.

Thanks. IIUC, both of the above approaches decode the sequences during
only shutdown. I'm wondering, why not periodically decode and
replicate the published sequences so that the decoding at the shutdown
will not take that longer? I can imagine a case where there are tens
of thousands of sequences in a production server, and surely decoding
and sending them just during the shutdown can take a lot of time
hampering the overall server uptime.

--
Bharath Rupireddy
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com