Re: Support logical replication of DDLs

Hello Alvaro,

> I think this is a pretty interesting and useful feature.
>
> Did you see some old code I wrote towards this goal?
> https://www.postgresql.org/message-id/20150215044814.GL3391@alvh.no-ip.org
> The intention was that DDL would produce some JSON blob that accurately
> describes the DDL that was run; the caller can acquire that and use it
> to produce working DDL that doesn't depend on runtime conditions. There
> was lots of discussion on doing things this way. It was ultimately
> abandoned, but I think it's valuable.

Thanks for pointing this out. I'm looking into it.

Hello Japin,
>The new patch change the behavior of publication, when we drop a table
>on publisher, the table also be dropped on subscriber, and this made the
>regression testa failed, since the regression test will try to drop the
>table on subscriber.

>IMO, we can disable the DDLs replication by default, which makes the
>regression test happy. Any thoughts?

Good catch, I forgot to run the whole TAP test suite. I think for now
we can simply disable DDL replication for the failing tests when
creating publication: $node_publisher->safe_psql('postgres',
"CREATE PUBLICATION tap_pub FOR ALL TABLES WITH (ddl='')");
I'll fix it in the next version of patch. I'll also work on breaking
down the patch into smaller pieces for ease of review.

Regards,
Zheng