Re: Logical replication from PG v13 and below to PG v14 (devel version) is not working.

On Fri, Sep 25, 2020 at 8:12 AM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>
> On Thu, Sep 24, 2020 at 6:33 PM Ashutosh Sharma <ashu(dot)coek88(at)gmail(dot)com> wrote:
> >
> > Hi Amit,
> >
> > > Here, I think instead of using MySubscription->stream, we should use
> > > server/walrecv version number as we used at one place in tablesync.c.
> >
> > Should subscribers be setting the LR protocol value based on what is
> > the publisher version it is communicating with or should it be set
> > based on whether streaming was enabled or not while creating that
> > subscription? AFAIU if we set this value based on the publisher
> > version (which is lets say >= 14), then it's quite possible that the
> > subscriber will start streaming changes for the in-progress
> > transactions even if the streaming was disabled while creating the
> > subscription, won't it?
> >
>
> No that won't happen because we send this option to the server
> (publisher in this case) only when version is >=14 and user has
> specified this option. See the below check in function
> libpqrcv_startstreaming()
> {
> ..
> if (options->proto.logical.streaming &&
> PQserverVersion(conn->streamConn) >= 140000)
> appendStringInfo(&cmd, ", streaming 'on'");
> ..
> }
>

Ah, okay, understood, thanks. So, that means we can use the streaming
protocol version if the server (publisher) supports it, regardless of
whether the client (subscriber) has the streaming option enabled or
not.

--
With Regards,
Ashutosh Sharma
EnterpriseDB:http://www.enterprisedb.com