Re: to_typemod(type_name) information function - Mailing list pgsql-hackers

On 2018-01-06 18:45:11 -0500, Tom Lane wrote:
> Sophie Herold <sophie_h@hemio.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.

As there's been no activity on this thread since this comment I'm
marking this returned with feedback. Sophie, are you planning to
implement something along these lines?

Greetings,

Andres Freund