Edit report at http://bugs.php.net/bug.php?id=48343&edit=1
ID: 48343
Comment by: rick at igabe dot us
Reported by: mikec at mikenz dot geek dot nz
Summary: Mysqlnd memory leak when fetching rows
Status: Bogus
Type: Bug
Package: MySQLi related
Operating System: *
PHP Version: 5.3CVS-2009-05-20 (snap)
New Comment:
This does seem to be related to mysqlnd only. However, it can become a
large
problem if many results are returned from a query. Each call to
mysql_fetch_assoc() for a single result set increases the memory used.
If the
memory limit is reached, the script dies with a fatal error. Switching
to
ext/mysql does not produce the problem. Is this really intended
behavior?
Previous Comments:
------------------------------------------------------------------------
[2009-05-24 18:08:57] johan...@php.net
Yes the memory calculation is now more precise and mysqlnd uses some own
caching so it will re use some of the memory on your next query.
------------------------------------------------------------------------
[2009-05-21 13:02:49] mikec at mikenz dot geek dot nz
Most of the memory is available again once it is destroyed. Very
similar between both versions.
The problem is that code which loops over large number of rows in php
5.2 with near constant memory usage now increase in memory usage as
it loops through the rows in 5.3 causing termination when they hit
the memory limit. Reported memory usage for a script in php 5.3 is a
lot higher than in php 5.2.
This bug may be bogus as mysqlnd uses php memory allocation so its
memory usage is now included in memory usage checks where libmysql's
memory usage in 5.2 was independent and uncounted. Can a developer
confirm? If so this should be noted in the PHP 5.3 upgrading notes or
migration information as it is unexpected at the moment.
------------------------------------------------------------------------
[2009-05-21 11:36:58] ninzya at inbox dot lv
Try destroying mysqli object before calculating estimated memory usage.
See what are results.
------------------------------------------------------------------------
[2009-05-20 05:56:05] mikec at mikenz dot geek dot nz
Description:
------------
A simple loop fetching rows from a database uses a lot more memory of
php5.3 when compared to php5.2.
First noticed on a Debian machine. Confirmed on a Windows machine with
latest snaps (20-May-2009). php.ini based on php.ini-dist/development
only change is to enable mysqli.
Reproduce code:
---------------
<?php
/**
Mysql test table:
CREATE TABLE `test` (
`id` int(11) NOT NULL auto_increment,
`value` int(11) NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1;
INSERT INTO `test` VALUES (1, 910044366),(2, 598209383),(3,
1057704306),(4, 877739287),(5, 260395243),(6, 1154353180),(7,
19390630),(8, 362285832),(9, 510459913),(10, 222644712),(11,
824641253),(12, 969677378),(13, 1131665776),(14, 263701992),(15,
409107462);
*/
$before = memory_get_usage();
echo "Memory Usage (in bytes)";
echo "\nBefore: " . $before;
$db = new mysqli("127.0.0.1", "test", "testpasswd", "test");
$result = $db->query('SELECT * FROM `test`');
$rows = 0;
while($result->fetch_array(MYSQLI_ASSOC)) {$rows++;}
$after = memory_get_usage();
echo "\nAfter: " . $after;
echo "\nDelta: " . ($after - $before);
echo "\nDelta per row: " . round(($after - $before)/$rows) . ' bytes per
row';
Expected result:
----------------
C:\test\php-5.2-nts-win32-VC6-x86-latest>php -v
PHP 5.2.10-dev (cli) (built: May 19 2009 11:46:39)
Copyright (c) 1997-2009 The PHP Group
Zend Engine v2.2.0, Copyright (c) 1998-2009 Zend Technologies
C:\test\php-5.2-nts-win32-VC6-x86-latest>php r:\dbmem.php
Memory Usage (in bytes)
Before: 55216
After: 56080
Delta: 864
Delta per row: 58 bytes per row
Actual result:
--------------
C:\test\php-5.3-nts-win32-VC9-x86-latest>php -v
PHP 5.3.0RC3-dev (cli) (built: May 19 2009 12:57:00)
Copyright (c) 1997-2009 The PHP Group
Zend Engine v2.3.0, Copyright (c) 1998-2009 Zend Technologies
C:\test\php-5.3-nts-win32-VC9-x86-latest>php r:\dbmem.php
Memory Usage (in bytes)
Before: 321328
After: 337384
Delta: 16056
Delta per row: 1070 bytes per row
Would expect the Delta per row to be the similar for PHP 5.3 but this is
no where near.
------------------------------------------------------------------------
--
Edit this bug report at http://bugs.php.net/bug.php?id=48343&edit=1
