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Re: Review: listagg aggregate

From: Thom Brown <thombrown(at)gmail(dot)com>
To: Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>
Cc: Takahiro Itagaki <itagaki(dot)takahiro(at)oss(dot)ntt(dot)co(dot)jp>, Robert Haas <robertmhaas(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, "David E(dot) Wheeler" <david(at)kineticode(dot)com>, "pgsql-hackers(at)postgresql(dot)org Hackers" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Review: listagg aggregate
Date: 2010-02-01 13:51:42
Message-ID: bddc86151002010551o26bfe392i8773ad07ebf71b9b@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-hackers
On 1 February 2010 13:40, Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> wrote:

> 2010/2/1 Thom Brown <thombrown(at)gmail(dot)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
>
>
>
Ah, I was looking at the expected results, and couldn't see a NULL outcome,
but then these aren't indicated in such results anyway.

Thom

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