From:
Operating system: Fedora Rawhide
PHP version: 5.3.6
Package: PDO related
Bug Type: Bug
Bug description:DBLIB segfaults when GROUPing with 0 rows for prepared
statements
Description:
------------
I haven't fully figured out the cause of this problem, but for what I can
narrow it down, it's a bit of a remote case.
What I am experiencing is odd behavior when doing a PDO(DBLIB) prepared
statement on a SELECT query with a GROUP BY clause. As far as I can tell,
when the query would have returned 0 results, the query returns an empty
array, but the next time the query is run, I get the following result
(regardless of what the data should actually be):
array(1) {
[0]=>
array(2) {
["!"]=>
NULL
[0]=>
NULL
}
}
After this occurs, any attempt (whether explicit or implicit) to unset the
statement results in a segfault in Zend/zend_alloc.c:2028:
if (ZEND_MM_IS_FREE_BLOCK(next_block)) {
I have also found that this only happens when the first execution of the
prepared statement results in a 0 row query. If the order of the execution
in the test script below is reversed so that a result is returned, the
prepared statement works fine from then on.
Another specific of this bug is that it only occurs with the GROUP BY
clause. The query will work fine if I have an aggregate function, but do
not have the GROUP BY column specified.
I have tried the query in a different query tool, and it works fine.
I also tried the script with the php5.3-201105231230 snapshot, but was
still having the issue.
This problem is similar to Bug #40639, but my problem seems more narrow in
focus. I also do not receive the same segfault as the other bug.
Test script:
---------------
<?php
$db = new PDO('dblib:host=server;dbname=db', 'user', 'pass');
$query = $db->prepare('SELECT COALESCE(SUM(tblTransaction.Amount), 0) FROM
tblTransaction INNER JOIN tblDiscount ON tblTransaction.TransactionTypeID =
tblDiscount.TransactionTypeID AND tblDiscount.DiscountID = :DiscountID
WHERE tblTransaction.Voided IS NULL AND tblTransaction.RegistrationID =
:RegistrationID GROUP BY tblTransaction.RegistrationID');
// This combination does not exist together in the database
$execute = $query->execute(array(':DiscountID' => 1, ':RegistrationID' =>
114));
echo "\nExecuted: " . ($execute ? 'Successful' : 'Failed') . "\n";
$results = $query->fetchAll();
var_dump($results);
// This combination does exist together in the database
$execute = $query->execute(array(':DiscountID' => 20, ':RegistrationID' =>
114));
echo 'Executed: ' . ($execute ? 'Successful' : 'Failed') . "\n";
$results = $query->fetchAll();
var_dump($results);
unset($query);
echo 'Unset';
Expected result:
----------------
Executed: Successful
array(0) {
}
Executed: Successful
array(1) {
[0]=>
array(2) {
["computed"]=>
string(4) "5.00"
[0]=>
string(4) "5.00"
}
}
Unset
Actual result:
--------------
Executed: Successful
array(0) {
}
Executed: Successful
array(1) {
[0]=>
array(2) {
["!"]=>
NULL
[0]=>
NULL
}
}
Segmentation fault (core dumped)
--
Edit bug report at http://bugs.php.net/bug.php?id=54908&edit=1
--
Try a snapshot (PHP 5.2):
http://bugs.php.net/fix.php?id=54908&r=trysnapshot52
Try a snapshot (PHP 5.3):
http://bugs.php.net/fix.php?id=54908&r=trysnapshot53
Try a snapshot (trunk):
http://bugs.php.net/fix.php?id=54908&r=trysnapshottrunk
Fixed in SVN:
http://bugs.php.net/fix.php?id=54908&r=fixed
Fixed in SVN and need be documented:
http://bugs.php.net/fix.php?id=54908&r=needdocs
Fixed in release:
http://bugs.php.net/fix.php?id=54908&r=alreadyfixed
Need backtrace:
http://bugs.php.net/fix.php?id=54908&r=needtrace
Need Reproduce Script:
http://bugs.php.net/fix.php?id=54908&r=needscript
Try newer version:
http://bugs.php.net/fix.php?id=54908&r=oldversion
Not developer issue:
http://bugs.php.net/fix.php?id=54908&r=support
Expected behavior:
http://bugs.php.net/fix.php?id=54908&r=notwrong
Not enough info:
http://bugs.php.net/fix.php?id=54908&r=notenoughinfo
Submitted twice:
http://bugs.php.net/fix.php?id=54908&r=submittedtwice
register_globals:
http://bugs.php.net/fix.php?id=54908&r=globals
PHP 4 support discontinued: http://bugs.php.net/fix.php?id=54908&r=php4
Daylight Savings: http://bugs.php.net/fix.php?id=54908&r=dst
IIS Stability:
http://bugs.php.net/fix.php?id=54908&r=isapi
Install GNU Sed:
http://bugs.php.net/fix.php?id=54908&r=gnused
Floating point limitations:
http://bugs.php.net/fix.php?id=54908&r=float
No Zend Extensions:
http://bugs.php.net/fix.php?id=54908&r=nozend
MySQL Configuration Error:
http://bugs.php.net/fix.php?id=54908&r=mysqlcfg
