From: | "Jim C(dot) Nasby" <jnasby(at)pervasive(dot)com> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | pgsql-hackers(at)postgreSQL(dot)org |
Subject: | Re: Supporting NULL elements in arrays |
Date: | 2005-11-09 01:02:22 |
Message-ID: | 20051109010221.GH19551@pervasive.com |
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Thread: | |
Lists: | pgsql-hackers |
On Tue, Nov 08, 2005 at 07:21:34PM -0500, Tom Lane wrote:
> I wrote:
> > ... the most straightforward thing to do is define an empty element
> > as meaning a NULL. But this might be objected to on a couple of grounds:
>
> I just thought of another, potentially fatal objection: it's ambiguous
> whether '{}'::text[] should be taken to mean an empty (zero-length)
> array or an array containing a single NULL element.
>
> For backwards compatibility it should mean an empty array, but then
> there's no way to represent ARRAY(NULL) in data dumps, which won't
> do either.
>
> The only workaround that comes to mind is to allow explicit
> specification of what's meant: '[1:1]{}' would be needed to represent
> the one-null case. Ugly.
Instead of bending over backwards to try and support older cases, would
a compatability mode be possible? Seems that would solve a lot of
problems.
--
Jim C. Nasby, Sr. Engineering Consultant jnasby(at)pervasive(dot)com
Pervasive Software http://pervasive.com work: 512-231-6117
vcard: http://jim.nasby.net/pervasive.vcf cell: 512-569-9461
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