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Re: Review: listagg aggregate

From: Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>
To: Thom Brown <thombrown(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 13:40:50
Message-ID: 162867791002010540q2a65b349u6c221fd3e821796a@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-hackers
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

>
> Thom
>
>

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