Date: Wed, 3 Jul 2013 16:06:52 -0400
From: Bruce Momjian <bruce@momjian.us>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Alvaro Herrera <alvherre@2ndquadrant.com>,
 Dev Kumkar <devdas.kumkar@gmail.com>,
 Thomas Kellerer <spam_eater@gmx.net>, pgsql-sql@postgresql.org
Subject: Re: Unquoted column names fold to lower case
Message-ID: <20130703200652.GD6492@momjian.us>
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On Wed, Jul  3, 2013 at 03:47:37PM -0400, Tom Lane wrote:
> Alvaro Herrera <alvherre@2ndquadrant.com> writes:
> > Dev Kumkar escribió:
> >> But what I am asking here is if an alias name is provided be it upper case,
> >> lower case, or a mix then shouldn't it be preserved as as it is given. All
> >> this talk is when alias names are unquoted, when quoted then its standard
> >> behavior as seen in other databases.
> 
> > Aliases are treated just like any other identifier.  The downcasing
> > happens in the lexer (src/backend/parser/scan.l), which is totally
> > unaware of the context in which this is happening; so there's no way to
> > tweak the downcasing behavior for only aliases and not other
> > identifiers.
> 
> Quite aside from implementation difficulty, restricting the change to
> just column aliases doesn't make it more palatable.  You'd entirely lose
> the argument that the change increases spec compliance, because the spec
> is perfectly clear that a column alias is an identifier just like any
> other.  And you'd still be paying a large part of the application
> breakage costs, because the identifiers coming back in query descriptors
> are one of the main ways applications would notice such a change.

And let's not forget that column aliases can be used as indentifiers in
queries:

	test=> SELECT 1 AS x
	test-> ORDER BY x;
	 x
	---
	 1
	(1 row)

	test=> SELECT 1 AS "X"
	ORDER BY x;
	ERROR:  column "x" does not exist
	LINE 2: ORDER BY x;

Changing this would mean that the same identifier would have different
case-folding rules depending on where it appeared in the query.

-- 
  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

  + It's impossible for everything to be true. +


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