Re: Support logical replication of DDLs

On Wed, Mar 29, 2023 at 10:23 PM Zheng Li <zhengli10(at)gmail(dot)com> wrote:
>
> On Wed, Mar 29, 2023 at 5:13 AM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> >
> > On Wed, Mar 29, 2023 at 2:49 AM Zheng Li <zhengli10(at)gmail(dot)com> wrote:
> > >
> > >
> > > I agree that a full fledged DDL deparser and DDL replication is too
> > > big of a task for one patch. I think we may consider approaching this
> > > feature in the following ways:
> > > 1. Phased development and testing as discussed in other emails.
> > > Probably support table commands first (as they are the most common
> > > DDLs), then the other commands in multiple phases.
> > > 2. Provide a subscription option to receive the DDL change, raise a
> > > notice and to skip applying the change. The users can listen to the
> > > DDL notice and implement application logic to apply the change if
> > > needed. The idea is we can start gathering user feedback by providing
> > > a somewhat useful feature (compared to doing nothing about DDLs), but
> > > also avoid heading straight into the potential footgun situation
> > > caused by automatically applying any mal-formatted DDLs.
> > >
> >
> > Doesn't this mean that we still need to support deparsing of such DDLs
> > which is what I think we don't want?
>
> I think we can send the plain DDL command string and the search_path
> if we don't insist on applying it in the first version. Maybe the
> deparser can be integrated later when we're confident that it's
> ready/subset of it is ready.
>

I think this will have overhead for users that won't need it and we
have to anyway remove it later when deparsing of such commands is
added. Personally, I don't think we need to do this to catch the apply
errors.

--
With Regards,
Amit Kapila.