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Re: array_agg() NULL Handling

From: Thom Brown <thom(at)linux(dot)com>
To: "David E(dot) Wheeler" <david(at)kineticode(dot)com>
Cc: PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: array_agg() NULL Handling
Date: 2010-09-01 06:56:58
Message-ID: AANLkTinWJ7w-w6K1Y156=gja25D2aNaLqURoMHcXQkPJ@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-hackers
On 1 September 2010 06:45, David E. Wheeler <david(at)kineticode(dot)com> wrote:
> The aggregate docs say:
>
>> The first form of aggregate expression invokes the aggregate across all input rows for which the given expression(s) yield non-null values. (Actually, it is up to the aggregate function whether to ignore null values or not — but all the standard ones do.)
>
> -- http://developer.postgresql.org/pgdocs/postgres/sql-expressions.html#SYNTAX-AGGREGATES
>
> That, however, is not true of array_agg():
>
> try=# CREATE TABLE foo(id int);
> CREATE TABLE
> try=# INSERT INTO foo values(1), (2), (NULL), (3);
> INSERT 0 4
> try=# select array_agg(id) from foo;
>  array_agg
> ──────────────
>  {1,2,NULL,3}
> (1 row)
>
> So are the docs right, or is array_agg() right?

I think it might be both.  array_agg doesn't return NULL, it returns
an array which contains NULL.

-- 
Thom Brown
Twitter: @darkixion
IRC (freenode): dark_ixion
Registered Linux user: #516935

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