Re: to_typemod(type_name) information function

Sophie Herold <sophie_h(at)hemio(dot)de> writes:
> the following patch allows to retrieve the typemod. Without this patch,
> it does not seem to be possible to generate the first column.

I thought about this a bit, and I now follow the problem you want to
solve, and agree that format_type() is going in the wrong direction.
However, the proposed solution seems a bit grotty. You're basically
always going to need to run parseTypeString twice on the same input,
because there are few if any use-cases for getting just the typmod
without the type OID. I think it might be more useful to provide
a single function

parse_type(type_name text, OUT typeid regtype, OUT typmod integer)

which would replace both to_regtype and to_typemod in your example.
Usage might look like

SELECT format_type(typeid, typmod)
FROM (VALUES
('INTERVAL SECOND (5)'),
('Varchar(17)'),
('timestamptz (2)')) AS x(t), parse_type(x.t);

Creating a function with multiple OUT parameters at the pg_proc.h level
is slightly painful, but see e.g. pg_sequence_parameters for a model.

regards, tom lane