Re: Add support for COPY TO in tablesync for partitioned tables.

On Wed, Nov 19, 2025 at 2:56 PM Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
>
> On Thu, Nov 13, 2025 at 7:17 PM Ajin Cherian <itsajin(at)gmail(dot)com> wrote:
> >
> > On Thu, Nov 13, 2025 at 8:49 AM Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
> > >
> > > On Mon, Nov 10, 2025 at 7:37 PM Ajin Cherian <itsajin(at)gmail(dot)com> wrote:
> > > >
> > > > On Tue, Nov 11, 2025 at 2:19 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> > > > >
> > > > > In the commit message, you mentioned: "Performance tests show it's
> > > > > faster than the COPY (SELECT ...) TO variant as it avoids the
> > > > > overheads of query processing and sending results to the COPY TO
> > > > > command.". Can you share the performance data to substantiate this
> > > > > point?
> > > > >
> > > >
> > > > This was based on the tests done in the original thread [1] and [2]
> > >
> > > Thank you for working on this item. I think it's a good follow-up
> > > patch for commit 4bea91f.
> > >
> > > Have you conducted any performance tests with logical replication
> > > setup? I've measured normal COPY TO cases but I think it would be
> > > worth checking how much the performance increase we can see in logical
> > > replication setup too.
> > >
> > Thanks for your interest in this patch.
> > I've tested the same setup as mentioned in [1] but with 10 tables and
> > 500 records each and measuring the total time it would take for all
> > the tablesync workers to finish sync (from log timings).
> > On the average:
> > Without patch
> > Tablesync time: 185.4 ms
> > Average COPY command times: 1.4168 ms
> >
> > With patch
> > Tablesync time: 172.2 ms (7% improvement)
> > Average COPY command times: 0.633 ms
> >
> > The improvement in performance is smaller as the table size increases.
> > There is better improvement for smaller tables.
> > Attaching my test scripts as well.
> >
>
> Thank you for the test! I've also done some performance tests and got
> similar results.
>
> The patch is pretty simple and looks good to me. I'll push the patch,
> barring objections.

Pushed.

Regards,

--
Masahiko Sawada
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