Re: Support logical replication of DDLs - Mailing list pgsql-hackers

On Thu, Apr 20, 2023 at 3:40 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
>
> On Thu, Apr 20, 2023 at 9:11 AM shveta malik <shveta.malik@gmail.com> wrote:
> >
> >
> > Few comments for ddl_deparse.c in patch dated April17:
>
> >
> > 6) There are plenty of places where we use 'append_not_present'
> > without using 'append_null_object'.
> > Do we need to have 'append_null_object' along with
> > 'append_not_present' at these places?
> >
>
> What is the difference if we add a null object or not before not_present?
>

Sorry I missed this question earlier. There is not much difference
execution wise, The "present": false' attribute is sufficient to
indicate that the expansion of that element is not needed when we
convert back json to ddl command. It is only needed for 'verbose'
mode. The 'append_null_object' call makes the format string complete
for the user to understand it better.  Example:

--without append_null_object, we get:
"collation": {"fmt": "COLLATE", "present": false}

--with  append_null_object, we get:
With append_null_object(tmp_obj, "%{name}D"), it is:
"collation": {"fmt": "COLLATE %{name}D", "name": null, "present": false}

So fmt:  "COLLATE %{name}D" is more complete (even though not needed
when the COLLATE clause is absent) and thus aligns to what we expect
out of verbose mode.

thanks
Shveta