From: Tom Lane <tgl@sss.pgh.pa.us>
To: Chuck McDevitt <cmcdevitt@greenplum.com>
Cc: Stephan Szabo <sszabo@megazone.bigpanda.com>
Cc: beau hargis <beauh@bluefrogmobile.com>
Cc: pgsql-sql@postgresql.org
Cc: pgsql-hackers@postgresql.org
Subject: Re: [HACKERS] Case Preservation disregarding case
Date: Wed, 01 Nov 2006 01:38:25 -0500
Message-ID: <14059.1162363105@sss.pgh.pa.us> (raw)
In-Reply-To: <EB48EBF3B239E948AC1E3F3780CF8F88012F8A53@MI8NYCMAIL02.Mi8.com>
References: <200610271623.37525.beauh@bluefrogmobile.com>
<1162003132.687.8.camel@pampa>
<200610301928.51255.beauh@bluefrogmobile.com>
<23177.1162265010@sss.pgh.pa.us>
<EB48EBF3B239E948AC1E3F3780CF8F88012F88DD@MI8NYCMAIL02.Mi8.com>
<24861.1162276496@sss.pgh.pa.us>
<EB48EBF3B239E948AC1E3F3780CF8F88012F89F8@MI8NYCMAIL02.Mi8.com>
<20061031101314.R83230@megazone.bigpanda.com>
<EB48EBF3B239E948AC1E3F3780CF8F88012F8A53@MI8NYCMAIL02.Mi8.com>
"Chuck McDevitt" <cmcdevitt@greenplum.com> writes:
> Equivalent, yes. But I can interpret that clause it mean I can show
> either the case folded or non-case-folded value in the information
> schema, as they are equivalent.
Well, that's an interesting bit of specs-lawyering, but I don't see
how you can defend it against these rules in SQL99 5.2:
21) For every <identifier body> IB there is exactly one
corresponding case-normal form CNF. CNF is an <identifier body>
derived from IB as follows.
Let n be the number of characters in IB. For i ranging from 1
(one) to n, the i-th character M(i) of IB is translated into the
corresponding character or characters of CNF as follows.
Case:
a) If M(i) is a lower case character or a title case character
for which an equivalent upper case sequence U is defined by
Unicode, then let j be the number of characters in U; the
next j characters of CNF are U.
b) Otherwise, the next character of CNF is M(i).
22) The case-normal form of the <identifier body> of a <regular
identifier> is used for purposes such as and including
determination of identifier equivalence, representation in
the Definition and Information Schemas, and representation in
diagnostics areas.
NOTE 44 - Any lower-case letters for which there are no upper-
case equivalents are left in their lower-case form.
Again, obviously we are not compliant because we fold to lower rather
than upper case, but I do not see how you can read (22) as not requiring
the information schema to show the upper-cased form. The output of
functions such as PQfname() might be considered closer to diagnostics
info than information schema, but that's covered too.
But the really serious problem with what you propose is that it would
allow two table columns with names that the system considers distinct
to show as the same string in the information schema and diagnostic
outputs. That can't be acceptable --- it's going to break any
application that does any nontrivial analysis of what it sees there,
not to mention that it violates various primary key constraints in
the information schema specification.
regards, tom lane
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To: pgsql-sql@postgresql.org
Cc: tgl@sss.pgh.pa.us, cmcdevitt@greenplum.com, sszabo@megazone.bigpanda.com, beauh@bluefrogmobile.com, pgsql-hackers@postgresql.org
Subject: Re: [HACKERS] Case Preservation disregarding case
In-Reply-To: <14059.1162363105@sss.pgh.pa.us>
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