Re: Review: listagg aggregate

Pavel Stehule <pavel.stehule@gmail.com>

From: Pavel Stehule <pavel.stehule@gmail.com>

To: Thom Brown <thombrown@gmail.com>

Cc: Takahiro Itagaki <itagaki.takahiro@oss.ntt.co.jp>, Robert Haas <robertmhaas@gmail.com>, Tom Lane <tgl@sss.pgh.pa.us>, "David E. Wheeler" <david@kineticode.com>, "pgsql-hackers@postgresql.org Hackers" <pgsql-hackers@postgresql.org>

Date: 2010-02-01T13:40:50Z

Lists: pgsql-hackers

2010/2/1 Thom Brown <thombrown@gmail.com>:
> I noticed that the regression test results don't include the following case:
>
> select string_agg(a) from (values(null),(null)) g(a);
>
> There is one similar where a delimiter is provided.
>
> Which leads me to ask for clarification, would it be safe to assume that
> string_agg can never itself return null?

if all values are null, then result is null.

Pavel

>
> Thom
>
>