On Sat, Sep 19, 2020 at 08:49:53PM -0400, Tom Lane wrote: > Bruce Momjian <br...@momjian.us> writes: > > test=> \df pg_get_keywords > > List > > of functions > > Schema | Name | Result data type | > > Argument data types | > > Type > > > > ------------+-----------------+------------------+-----------------------------------------------------------------------------------------------+------ > > pg_catalog | pg_get_keywords | SETOF record | OUT word text, OUT > > catcode "char", OUT barelabel boolean, OUT catdesc text, OUT baredesc text > > | func > > (1 row) > > > test=> select * from pg_get_keywords() AS f(word text); > > --> ERROR: a column definition list is only allowed for functions > > returning "record" > > LINE 1: select * from pg_get_keywords() AS f(word text); > > Yeah, this error message needs some help. With a function having > multiple OUT parameters, the prorettype is indeed "record", but > the specific record type is implied by the OUT parameters so you > do not need to (and can't) specify it in the query. > > The point of the AS feature is to allow specifying the concrete > record type for record-returning functions that don't have a > predefined result record type, like dblink(). > > I think this error text was written before we had multiple OUT > parameters, so it was okay at the time; but now it needs to be > more precise.
OK, thanks. It seems this area needs some work, in general. Unfortunately I don't see any system functions that return RECORD and don't use OUT parameters, except dblink(), json(b)_to_record(), json(b)_to_recordset(), and record_*. This is going to be hard to illustrate. :-( I did get this working: test=> select * FROM json_to_record('{"a": 1, "b": 2}'::json) as (b text); b --- 2 but doing this to illustrate ROWS FROM is going to be complex. -- Bruce Momjian <br...@momjian.us> https://momjian.us EnterpriseDB https://enterprisedb.com The usefulness of a cup is in its emptiness, Bruce Lee