Re: Support logical replication of DDLs, take2

On Mon, Apr 27, 2026 at 11:45 AM Dilip Kumar <dilipbalaut(at)gmail(dot)com> wrote:
>
> On Tue, Apr 21, 2026 at 4:45 AM Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
> >
> > The overall idea of the previous patch set was to implement DDL
> > deparsing and utilize it for DDL replication. It converted a parse
> > tree into a JSON string. For instance, if a user executes "DROP TABLE
> > t1", the deparser generates from its parse tree:
> >
> > {DROPSTMT :objects (("t1")) :removeType 41 :behavior 0 :missing_ok
> > false :concurrent false}
> >
> > to:
> >
> > {"fmt": "DROP TABLE %{objidentity}s", "objidentity": "public.t1"}
> >
> > This JSON string is self-documenting, meaning someone who gets it can
> > easily reconstruct the original DDL with schema-qualified object
> > names. In a dedicated event trigger for logical replication, we
> > deparsed the parse tree of a DDL, wrote it into a WAL record, and then
> > the logical decoding processed it similarly to DML changes.
>
> I think there was also a discussion on whether to use JSON vs the
> existing infrastructure of converting nodes to strings. Although the
> JSON is standard format and might provide more flexibility using
> existing format avoid extra maintence burden.
>

Yes, the discussion related to node-to-string and the pros and cons of
the deparse approach are detailed in email [1]. I think some of these
points could be also related to the new approach as well.

[1] - https://www.postgresql.org/message-id/OS0PR01MB571684CBF660D05B63B4412C94AB9%40OS0PR01MB5716.jpnprd01.prod.outlook.com

--
With Regards,
Amit Kapila.