Re: logical replication empty transactions

On Tue, Feb 8, 2022 at 5:27 AM osumi(dot)takamichi(at)fujitsu(dot)com
<osumi(dot)takamichi(at)fujitsu(dot)com> wrote:
>
> On Friday, August 13, 2021 8:01 PM Ajin Cherian <itsajin(at)gmail(dot)com> wrote:
> > On Mon, Aug 2, 2021 at 7:20 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>
> > wrote:
> Changing the timing to send the keepalive to the decoding commit
> timing didn't look impossible to me, although my suggestion
> can be ad-hoc.
>
> After the initialization of sentPtr(by confirmed_flush lsn),
> sentPtr is updated from logical_decoding_ctx->reader->EndRecPtr in XLogSendLogical.
> In the XLogSendLogical, we update it after we execute LogicalDecodingProcessRecord.
> This order leads to the current implementation to wait the next iteration
> to send a keepalive in WalSndWaitForWal.
>
> But, I felt we can utilize end_lsn passed to ReorderBufferCommit for updating
> sentPtr. The end_lsn is the lsn same as the ctx->reader->EndRecPtr,
> which means advancing the timing to update the sentPtr for the commit case.
> Then if the transaction is empty in synchronous mode,
> send the keepalive in WalSndUpdateProgress directly,
> instead of having the force_keepalive_syncrep flag and having it true.
>

You have a point in that we don't need to delay sending this message
till next WalSndWaitForWal() but I don't see why we need to change
anything about update of sentPtr.

--
With Regards,
Amit Kapila.