Re: Allow logical replication to copy tables in binary format

Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, 16 Mar 2023 Per, 06:25 tarihinde
şunu yazdı:

> On Thu, Mar 16, 2023 at 8:27 AM Euler Taveira <euler(at)eulerto(dot)com> wrote:
> >
> > On Wed, Mar 8, 2023, at 11:50 PM, Amit Kapila wrote:
> >
> > It is not clear to me which version check you wanted to add because we
> > seem to have a binary option in COPY from the time prior to logical
> > replication. I feel we need a publisher version 14 check as that is
> > where we start to support binary mode transfer in logical replication.
> > See the check in function libpqrcv_startstreaming().
> >
> > ... then you are breaking existent cases. Even if you have a convincing
> > argument, you are introducing a behavior change in prior versions (commit
> > messages should always indicate that you are breaking backward
> compatibility).
> >
> > +
> > + /*
> > + * The binary option for replication is supported since v14
> > + */
> > + if (walrcv_server_version(LogRepWorkerWalRcvConn) >= 140000 &&
> > + MySubscription->binary)
> > + {
> > + appendStringInfo(&cmd, " WITH (FORMAT binary)");
> > + options = lappend(options, makeDefElem("format", (Node *)
> makeString("binary"), -1));
> > + }
> > +
> >
> > What are the arguments to support since v14 instead of the to-be-released
> > version? I read the thread but it is not clear. It was said about the
> > restrictive nature of this feature and it will be frustrating to see
> that the
> > same setup (with the same commands) works with v14 and v15 but it
> doesn't with
> > v16.
> >
>
> If the failure has to happen it will anyway happen later when the
> publisher will be upgraded to v16. The reason for the version checks
> as v14 was to allow the initial sync from the same version where the
> binary mode for replication was introduced. However, if we expect
> failures in the existing setup, I am fine with supporting this for >=
> v16.
>

Upgrading the subscriber to v16 and keeping the subscriber in v14 could
break existing subscriptions. I don't know how likely such a case is.

I don't have a strong preference on this. What do you think? Should we
change it >=v16 or keep it as it is?

Best,
--
Melih Mutlu
Microsoft