Re: Support logical replication of DDLs

On Wed, May 11, 2022 at 6:25 PM Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
>
> On Wed, May 11, 2022 at 6:15 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> >
> > On Wed, May 11, 2022 at 1:09 PM Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
> > >
> > > On Mon, May 9, 2022 at 6:05 PM Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> wrote:
> > > >
> > > >
> > > > The code in test_ddl_deparse is a pretty lame start, not nearly good
> > > > enough by a thousand miles. My real intention was to have a test
> > > > harness that would first run a special SQL script to install DDL
> > > > capture, then run all the regular src/test/regress scripts, and then at
> > > > the end ensure that all the DDL scripts were properly reproduced -- for
> > > > example transmit them to another database, replay them there, and dump
> > > > both databases and compare them. However, there were challenges which I
> > > > no longer remember and we were unable to complete this, and we are where
> > > > we are.
> > >
> > > I think the regression test suite improvements in these few years make
> > > it easier to implement such regression tests in order to check not
> > > only the existing commands but also future changes. I'll try it if no
> > > one is working on it, and let us see if there are challenges.
> > >
> >
> > I think it is a good idea to give it a try. However, one point to note
> > in this regard is that if we decide to use deparsing for DDL logical
> > replication then the tests for logical replication will automatically
> > test all the deparsing code.
>
> Do you mean that in tests for logical replication we run regression
> tests on the publisher and check if relations are
> created/altered/dropped expectedly on the subscriber?
>

Yes.

> If we rely on
> tests for logical replication, I think logical replication will have
> to support all future DDL changes/features.
>

Agreed, so we can't completely rely on logical replication tests.

--
With Regards,
Amit Kapila.