Re: [PATCH] pg_get_domain_ddl: DDL reconstruction function for CREATE DOMAIN statement

Hi Haritabh, Tom,

Thanks for the thorough review. v8 fixes all reported bugs and adds
round-trip tests to address the forcing-function concern.

Haritabh's bugs — all fixed in attached v8.

On 19/02/26 01:10, Tom Lane wrote:

> This report crystallized something that's been bothering me
> about not only pg_get_domain_ddl() but all the similar patches
> that are in the queue. They are adding a large amount of new
> code that will have to be kept in sync with behavior elsewhere
> and there is basically zero forcing function to ensure that
> that happens. Even the rather-overly-voluminous test cases
> proposed for the functions cannot catch errors of omission,
> especially not future errors of omission.

v8 adds a PL/pgSQL round-trip harness that captures DDL, drops
the domain, re-executes the DDL, and ASSERTs the regenerated DDL
is identical, any suggestions on how to improve it are welcomed.
This function can be re-used also with other get_<object>_ddl
as it accepts a parameter for the <object_type>, this way we can
use some common code.

> I don't really know what to do about this, but I don't like the
> implementation approach that's being proposed. I think it's
> loading too much development effort and future maintenance effort
> onto us in comparison to the expected benefit of having these
> functions.

I understand your point that there are multiple implementations
and each have its own way of doing it. I think we should start
somewhere and eventually ask further implementations to adapt to
use common code or make it work with all existing (at that point)
implementations, one at a time.
pg_get_domain_ddl implementation uses mainly common code in ruleutils.c
plus some glue code. We could maybe also create a new separate
module and put all the code for all these features there.

What do you think?

Cheers,
Florin

--
*Florin Irion*
www.enterprisedb.com <https://www.enterprisedb.com>