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BUG #6270: Invalid string comparison if the string contains '+' or '-' sign.

From: "Evgeniy Galkin" <unikoid(at)gmail(dot)com>
To: pgsql-bugs(at)postgresql(dot)org
Subject: BUG #6270: Invalid string comparison if the string contains '+' or '-' sign.
Date: 2011-10-25 15:37:59
Message-ID: 201110251537.p9PFbxVn000209@wwwmaster.postgresql.org (view raw or flat)
Thread:
Lists: pgsql-bugs
The following bug has been logged online:

Bug reference:      6270
Logged by:          Evgeniy Galkin
Email address:      unikoid(at)gmail(dot)com
PostgreSQL version: 9.0.4
Operating system:   GNU/Linux (Ubuntu 10.10)
Description:        Invalid string comparison if the string contains '+' or
'-' sign.
Details: 

I'm running postgresql 9.0.4 on GNU/Linux system.
I'm trying to compare two strings which are starting with '+' and '-' signs.
And there is some strange behaviour.

Example:
Query "SELECT '+' > '-';" returns t (true), but "SELECT '+1' > '-2';"
returns f (false). And query "SELECT ascii('+') > ascii('-');" returns f as
it should be, so saying that '+' > '-' is true probably is not valid
result.

More complex example:
db=> create table tbl_tmp (a text); insert into tbl_tmp values ('+'), ('-'),
('+1'), ('+2'), ('+3'), ('-1'), ('-2'), ('-3'); select * from tbl_tmp order
by a;
CREATE TABLE
INSERT 0 8
 a  
----
 -
 +
 -1
 +1
 -2
 +2
 -3
 +3
(8 rows)


This behaviour is also appeared on postgresql 9.1.1 on ubuntu 11.10, but the
same version of psql on Mac OS X Lion works as expected ("SELECT '+' > '-';"
returns f and example with order by gives at first values that are starting
with '+' and at last that are starting with '-' sign).

So, I think that it can be GNU/Linux (maybe glibc) related bug.

Sorry for probably ugly English or if it is duplication of well known issue.

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