From: Bruce Momjian <pgman@candle.pha.pa.us>
Message-Id: <200506250150.j5P1oNO01032@candle.pha.pa.us>
Subject: Re: [SQL] ARRAY() returning NULL instead of ARRAY[]
In-Reply-To: <1118074367.5506.16.camel@dicaprio.akademie1.de>
To: "Markus Bertheau ?" <twanger@bluetwanger.de>
Date: Fri, 24 Jun 2005 21:50:23 -0400 (EDT)
Cc: Joe Conway <mail@joeconway.com>, pgsql-hackers@postgresql.org,
	Tom Lane <tgl@sss.pgh.pa.us>
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Is this a TODO item?

---------------------------------------------------------------------------

Markus Bertheau ? wrote:
> ? ???, 06/06/2005 ? 08:58 -0700, Joe Conway ?????:
> > Joe Conway wrote:
> > > Actually, consistent with my last post, I think array_upper() on a 
> > > zero-element array should return NULL. A zero-element array has a 
> > > defined lower bound, but its upper bound is not zero -- it is really 
> > > undefined.
> > 
> > Just to clarify my response, this is what I propose:
> > 
> > regression=# select array_upper('[2][1:]={{},{}}'::int[],1);
> >   array_upper
> > -------------
> >             2
> > (1 row)
> > 
> > regression=# select array_upper('[2][1:]={{},{}}'::int[],2) IS NULL;
> >   ?column?
> > ----------
> >   t
> > (1 row)
> 
> Hmm, this gets really complicated and inconsistent. Complicated means
> unusable. What about modifying the dimension syntax such that the second
> number means number of elements instead of upper bound? That particular
> problem would go away then, and array_upper('[0:0]={}'::int[]) can
> return the correct 0 then.
> 
> What I'm actually worrying about is that array_upper(array(select 1
> where false)) returns 0.
> 
> An option would be to drop the possibility to let the array start at
> another index than 0. I don't know why it was decided to do that in the
> first place. It seems a rather odd feature to me.
> 
> Markus
> -- 
> Markus Bertheau ? <twanger@bluetwanger.de>
> 
> 
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