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To: Markus Bertheau =?UTF-8?Q?=E2=98=AD?= <twanger@bluetwanger.de>
Cc: Joe Conway <mail@joeconway.com>, pgsql-sql@postgresql.org,
	pgsql-hackers@postgresql.org
Subject: Re: ARRAY() returning NULL instead of ARRAY[] resp. {} 
In-reply-to: <1118067445.5506.6.camel@dicaprio.akademie1.de> 
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Comments: In-reply-to Markus Bertheau =?UTF-8?Q?=E2=98=AD?=
	<twanger@bluetwanger.de>
	message dated "Mon, 06 Jun 2005 16:17:24 +0200"
Date: Mon, 06 Jun 2005 10:44:49 -0400
Message-ID: <25974.1118069089@sss.pgh.pa.us>
From: Tom Lane <tgl@sss.pgh.pa.us>
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Markus Bertheau =?UTF-8?Q?=E2=98=AD?= <twanger@bluetwanger.de> writes:
> By analogy, array_upper('{}'::TEXT[], 1) should return 0 instead of
> NULL.

No, that doesn't follow ... we've traditionally considered '{}' to
denote a zero-dimensional array.  A 1-D array of no elements is
'[1:0]={}', just as Joe shows ... or at least it would be except
for an overenthusiastic error check:

regression=# select '[1:0]={}' :: int[];
ERROR:  upper bound cannot be less than lower bound

I think this should be a legal boundary case.  In general, it should be
possible to form zero-size arrays of any number of dimensions.

			regards, tom lane