Skip site navigation (1) Skip section navigation (2)

Re: [HACKERS] Case Preservation disregarding case

From: "Chuck McDevitt" <cmcdevitt(at)greenplum(dot)com>
To: "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: "beau hargis" <beauh(at)bluefrogmobile(dot)com>,pgsql-sql(at)postgresql(dot)org,pgsql-hackers(at)postgresql(dot)org
Subject: Re: [HACKERS] Case Preservation disregarding case
Date: 2006-10-31 17:11:16
Message-ID: EB48EBF3B239E948AC1E3F3780CF8F88012F89F8@MI8NYCMAIL02.Mi8.com (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-sql
We treated quoted identifiers as case-specific, as the spec requires.

In the catalog, we stored TWO columns... The column name with case
converted as appropriate (as PostgreSQL already does), used for looking
up the attribute,
And a second column, which was the column name with the case exactly as
entered by the user.

So, your example would work just fine.


-----Original Message-----
From: Tom Lane [mailto:tgl(at)sss(dot)pgh(dot)pa(dot)us] 
Sent: Monday, October 30, 2006 10:35 PM
To: Chuck McDevitt
Cc: beau hargis; pgsql-sql(at)postgresql(dot)org; pgsql-hackers(at)postgresql(dot)org
Subject: Re: [HACKERS] [SQL] Case Preservation disregarding case
sensitivity?

"Chuck McDevitt" <cmcdevitt(at)greenplum(dot)com> writes:
> At Teradata, we certainly interpreted the spec to allow
case-preserving,
> but case-insensitive, identifiers.

Really?

As I see it, the controlling parts of the SQL spec are (SQL99 sec 5.2)

        26) A <regular identifier> and a <delimited identifier> are
            equivalent if the <identifier body> of the <regular
identifier>
            (with every letter that is a lower-case letter replaced by
the
            corresponding upper-case letter or letters) and the
<delimited
            identifier body> of the <delimited identifier> (with all
            occurrences of <quote> replaced by <quote symbol> and all
            occurrences of <doublequote symbol> replaced by <double
quote>),
            considered as the repetition of a <character string literal>
            that specifies a <character set specification> of
SQL_IDENTIFIER
            and an implementation-defined collation that is sensitive to
            case, compare equally according to the comparison rules in
            Subclause 8.2, "<comparison predicate>".

        27) Two <delimited identifier>s are equivalent if their
<delimited
            identifier body>s, considered as the repetition of a
<character
            string literal> that specifies a <character set
specification>
            of SQL_IDENTIFIER and an implementation-defined collation
            that is sensitive to case, compare equally according to the
            comparison rules in Subclause 8.2, "<comparison predicate>".

Note well the "sensitive to case" bits there.  Now consider

	CREATE TABLE tab (
		"foobar" int,
		"FooBar" timestamp,
		"FOOBAR" varchar(3)
	);

We can *not* reject this as containing duplicate column names, else we
have certainly violated rule 27.  Now what will you do with

	SELECT fooBar FROM tab;

?  The spec is unquestionably on the side of "you selected the varchar
column"; historical Postgres practice is on the side of "you selected
the int column".  AFAICS a case-insensitive approach would have to
fail with some "I can't identify which column you mean" error.  I am
interested to see where you find support for that in the spec...

			regards, tom lane



In response to

Responses

pgsql-hackers by date

Next:From: Chuck McDevittDate: 2006-10-31 17:13:31
Subject: Re: [HACKERS] Case Preservation disregarding case
Previous:From: Teodor SigaevDate: 2006-10-31 16:53:07
Subject: Re: [HACKERS] Index greater than 8k

pgsql-sql by date

Next:From: Chuck McDevittDate: 2006-10-31 17:13:31
Subject: Re: [HACKERS] Case Preservation disregarding case
Previous:From: BeemerBikerDate: 2006-10-31 17:01:27
Subject: refining view using temp tables

Privacy Policy | About PostgreSQL
Copyright © 1996-2014 The PostgreSQL Global Development Group