From: Bruce Momjian <bruce@momjian.us>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: David G. Johnston <david.g.johnston@gmail.com>
Cc: Guyren Howe <guyren@gmail.com>
Cc: Pg Docs <pgsql-docs@lists.postgresql.org>
Subject: Re: Please provide examples of rows from
Date: Sat, 19 Sep 2020 21:38:46 -0400
Message-ID: <20200920013846.GC22746@momjian.us> (raw)
In-Reply-To: <798909.1600562993@sss.pgh.pa.us>
References: <158638264419.662.2482095087061084020@wrigleys.postgresql.org>
<20200904014618.GB13932@momjian.us>
<CAKFQuwbBDr22KJRyJQRECO_XU6cyouwz3ocn0Tv4JgG4Gm5hMQ@mail.gmail.com>
<20200920003910.GA22746@momjian.us>
<798909.1600562993@sss.pgh.pa.us>
On Sat, Sep 19, 2020 at 08:49:53PM -0400, Tom Lane wrote:
> Bruce Momjian <bruce@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 <bruce@momjian.us> https://momjian.us
EnterpriseDB https://enterprisedb.com
The usefulness of a cup is in its emptiness, Bruce Lee
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Subject: Re: Please provide examples of rows from
In-Reply-To: <20200920013846.GC22746@momjian.us>
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