Re: Review: listagg aggregate

Robert Haas <robertmhaas@gmail.com>

From: Robert Haas <robertmhaas@gmail.com>

To: Tom Lane <tgl@sss.pgh.pa.us>

Cc: "David E. Wheeler" <david@kineticode.com>, Pavel Stehule <pavel.stehule@gmail.com>, Peter Eisentraut <peter_e@gmx.net>, Scott Bailey <artacus@comcast.net>, "pgsql-hackers@postgresql.org Hackers" <pgsql-hackers@postgresql.org>

Date: 2010-01-26T18:15:15Z

Lists: pgsql-hackers

On Tue, Jan 26, 2010 at 12:36 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> "David E. Wheeler" <david@kineticode.com> writes:
>> Because it's an aggregate that cocatenates values. It's not an
>> aggregate that lists things. I also like concat_agg better than
>> string_agg because it's not limited to acting on strings.
>
> But what it *produces* is a string.  For comparison, the
> SQL-standard-specified array_agg produces arrays, but what it
> acts on isn't an array.

This point is well-taken, but naming it string_agg() because it
produces a string doesn't seem quite descriptive enough.  We might
someday (if we don't already) have a number of aggregates that produce
an output that is a string; we can't name them all by the output type.

...Robert