Re: BUG #4509: array_cat's null behaviour is inconsistent

Added to TODO:

    Improve handling of NULLs in arrays

        * http://archives.postgresql.org/pgsql-bugs/2008-11/msg00009.php

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Kevin Field wrote:
>
> The following bug has been logged online:
>
> Bug reference:      4509
> Logged by:          Kevin Field
> Email address:      kev@brantaero.com
> PostgreSQL version: 8.3.4
> Operating system:   Windows Server 2003 SP2
> Description:        array_cat's null behaviour is inconsistent
> Details:
>
> Section 9.2 in the docs say, 'The ordinary comparison operators yield null
> (signifying "unknown") when either input is null.'  This applies to other
> operators too.  For example, the result of tacking an unknown value onto a
> known one is unknown, because you don't know what exactly you just tacked
> on.  So
>
>    select null::text || 'hello';
>
> ...returns NULL, which makes sense.  But then this
>
>    select array_cat(null::integer[], '{3}'::integer[]);
>
> ...doesn't return NULL, which it should, for consistency.
>
> Kev
>
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