Re: Support logical replication of DDLs

On Sat, May 7, 2022 at 9:38 AM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>
> On Fri, May 6, 2022 at 10:21 PM Zheng Li <zhengli10(at)gmail(dot)com> wrote:
> >
> > > Attached is a set of two patches as an attempt to evaluate this approach.
> > >
> >
> > Thanks for exploring this direction.
> >
> > I read the deparsing thread and your patch. Here is my thought:
> > 1. The main concern on maintainability of the deparsing code still
> > applies if we want to adapt it for DDL replication.
> >
>
> I agree that it adds to our maintainability effort, like every time we
> enhance any DDL or add a new DDL that needs to be replicated, we
> probably need to change the deparsing code. But OTOH this approach
> seems to provide better flexibility. So, in the long run, maybe the
> effort is worthwhile. I am not completely sure at this stage which
> approach is better but I thought it is worth evaluating this approach
> as Alvaro and Robert seem to prefer this idea.

+1, IMHO with deparsing logic it would be easy to handle the mixed DDL
commands like ALTER TABLE REWRITE. But the only thing is that we will
have to write the deparsing code for all the utility commands so there
will be a huge amount of new code to maintain.

> > 2. The search_path and role still need to be handled, in the deparsing
> > code. And I think it's actually more overhead to qualify every object
> > compared to just logging the search_path and enforcing it on the apply
> > worker.
> >
>
> But doing it in the deparsing code will have the benefit that the
> other plugins won't have to develop similar logic.

Right, this makes sense.

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