MySQL Bugs: #26051: XML: ExtractValue() returns wrong results for boolean() XPath test

Bug #26051	XML: ExtractValue() returns wrong results for boolean() XPath test
Submitted:	3 Feb 2007 18:23	Modified:	21 Jul 2008 9:38
Reporter:	Marcin Kurzyna	Email Updates:
Status:	Closed	Impact on me:	None
Category:	MySQL Server: XML functions	Severity:	S3 (Non-critical)
Version:	5.1.14	OS:	Linux (Linux)
Assigned to:	Alexander Barkov	CPU Architecture:	Any
Tags:	ExtractValue, XML, XPath

Description:
The boolean() XPath test returns false for all tests where node count > 1. According to http://www.w3.org/TR/xpath#section-Boolean-Functions boolean() should return true for non empty node-sets.

This is tested on server with applyed patch for bug #24747 
(XML node axes access).

How to repeat:
mysql> set @xml = '<r><n id="1">v</n><n id="2">v</n></r>';
Query OK, 0 rows affected (0.00 sec)

Ex1: Error for more then one node in result-set:
----------------------------------------------------------------

mysql> SELECT ExtractValue(@xml,'boolean(//n)') AS WrongResult;
+--------------+
| WrongResult |
+--------------+
| 0            |
+--------------+
1 row in set (0.00 sec)

mysql> SELECT ExtractValue(@xml,'count(//n)') AS CorrectResult;
+---------------+
| CorrectResult |
+---------------+
| 2             |
+---------------+
1 row in set (0.00 sec)

Ex2: Correct for one node in result-set:
----------------------------------------------------------------

mysql> SELECT ExtractValue(@xml,'boolean(//n[@id=1])') AS CorrectResult;
+---------------+
| CorrectResult |
+---------------+
| 1             |
+---------------+
1 row in set (0.00 sec)

mysql> SELECT ExtractValue(@xml,'count(//n[@id=1])') AS CorrectResult;
+---------------+
| CorrectResult |
+---------------+
| 1             |
+---------------+
1 row in set (0.00 sec)

Ex3: Correct for no node in result-set:
----------------------------------------------------------------

mysql> SELECT ExtractValue(@xml,'boolean(//n[@id=3])') AS CorrectResult;
+---------------+
| CorrectResult |
+---------------+
| 0             |
+---------------+
1 row in set (0.00 sec)

mysql> SELECT ExtractValue(@xml,'count(//n[@id=3])') AS CorrectResult;
+---------------+
| CorrectResult |
+---------------+
| 0             |
+---------------+
1 row in set (0.00 sec)

Thank you for the report.

Verified as described on Linux using last developers sources.

The second part of this problem is that boolean cast form strings
does not work well:

mysql> SELECT ExtractValue('<r></r>','boolean("00")') as WrongResult;
+-------------+
| WrongResult |
+-------------+
| 0           |
+-------------+
1 row in set (2.17 sec)

mysql> SELECT ExtractValue('<r></r>','boolean("11")') as CorrectResult;
+---------------+
| CorrectResult |
+---------------+
| 1             |
+---------------+
1 row in set (1.09 sec)

It must work this way:

"a string is true if and only if its length is non-zero"

so both queries must return 1.

A patch for this bug has been committed. After review, it may
be pushed to the relevant source trees for release in the next
version. You can access the patch from:

  http://lists.mysql.com/commits/34883

ChangeSet@1.2569, 2007-10-04 14:40:27+05:00, bar@mysql.com +3 -0
  Bug#26051 XML: ExtractValue() returns wrong results for boolean() XPath test
  Problem: boolean cast didn't work well in some cases:
  - node sets consisting of more than one nodes
  - strings
  Fix: making boolean cast work accoring to XPath specifications:
  - return true for any non-empty node sets
  - return true for any non-empty strings

A patch for this bug has been committed. After review, it may
be pushed to the relevant source trees for release in the next
version. You can access the patch from:

  http://lists.mysql.com/commits/44505

ChangeSet@1.2574, 2008-03-27 14:57:06+04:00, bar@mysql.com +3 -0
  Bug#26051 XML: ExtractValue() returns wrong results for boolean() XPath test
  Problem: boolean cast didn't work well in some cases:
  - node sets consisting of more than one nodes
  - strings
  Fix: making boolean cast work accoring to XPath specifications:
  - return true for any non-empty node sets
  - return true for any non-empty strings
  - return 0 for NULL strings

Pushed into 5.1.24-engines

Merged into bzr mysql-6.0.7

Documented bugfix in the 5.1.24 and 6.0.7 changelogs. Noted issues in XML Functions section of 5.1 and 6.0 Manual. Closed.

Pushed into 6.0.6-alpha  (revid:sp1r-bar@mysql.com/bar.myoffice.izhnet.ru-20080327105706-41158) (version source revid:hakan@mysql.com-20080716160034-sdexuyp3qow7zlc6) (pib:3)