Re: Support logical replication of DDLs

On Sun, May 8, 2022 at 12:39 PM Dilip Kumar <dilipbalaut(at)gmail(dot)com> wrote:
>
> 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.

I haven't gone through the entire thread, just trying to understand
the need of deparsing logic - do we need the DDL query text to be sent
to subscribers? If yes, why can't we WAL log the DDL query text as-is
and the logical decoding can send those to subscribers, as-is or in a
modified form? Or log the DDLs to a separate log on disk?

Regards,
Bharath Rupireddy.