Re: Support logical replication of DDLs

On Mon, Mar 21, 2022 at 1:43 PM Dilip Kumar <dilipbalaut(at)gmail(dot)com> wrote:
>
> On Thu, Mar 17, 2022 at 2:47 AM Zheng Li <zhengli10(at)gmail(dot)com> wrote:
> >
> > Hi,
> >
> > >If you don't mind, would you like to share the POC or the branch for this work?
> >
> > The POC patch is attached. It currently supports the following functionalities:
>
> Thanks for sharing, I will look into it.
>
> > >In such cases why don't we just log the table creation WAL for DDL
> > >instead of a complete statement which creates the table and inserts
> > >the tuple? Because we are already WAL logging individual inserts and
> > >once you make sure of replicating the table creation I think the exact
> > >data insertion on the subscriber side will be taken care of by the
> > >insert WALs no?
> >
> > The table creation WAL and table insert WAL are available. The tricky
> > part is how do we break down this command into two parts (a normal
> > CREATE TABLE followed by insertions) either from the parsetree or the
> > WALs. I’ll have to dig more on this.
>
> I agree that this is a bit tricky, anyway I will also put more thoughts on this.

I had put some more thought about this, basically, during CTAS we are
generating the CreateStmt inside "create_ctas_internal" and executing
it first before inserting the tuple, so can't we generate the
independent sql just for creating the tuple maybe using deparsing or
something?

Apart from that I have one more question, basically if you are
directly logging the sql query then how you are identifying under
which schema you need to create that table, are you changing the sql
and generating schema-qualified name?

--
Regards,
Dilip Kumar
EnterpriseDB: http://www.enterprisedb.com