Bug #77308 [Opn]: Unbuffered queries memory leak

From: Date: Wed, 02 Jan 2019 10:58:17 +0000
Subject: Bug #77308 [Opn]: Unbuffered queries memory leak
References: 1  Groups: php.bugs 
Request: Send a blank email to php-bugs+get-218737@lists.php.net to get a copy of this message 
Edit report at https://bugs.php.net/bug.php?id=77308&edit=1

 ID:                 77308
 Updated by:         nikic@php.net
 Reported by:        sjon at hortensius dot net
 Summary:            Unbuffered queries memory leak
 Status:             Open
 Type:               Bug
 Package:            MySQL related
 Operating System:   archlinux
 PHP Version:        7.3.0
 Block user comment: N
 Private report:     N

 New Comment:

Test script including (slow) table generation:

<?php
ini_set('memory_limit', '8M');

$pdo = new PDO('mysql:host=127.0.0.1;dbname=test', 'php-test',
'password');
$pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
$pdo->setAttribute(PDO::MYSQL_ATTR_USE_BUFFERED_QUERY, false);

$pdo->exec("DROP TABLE IF EXISTS large_table");
$pdo->exec("CREATE TABLE large_table (id int)");
for ($j = 0; $j < 100; $j++) {
    $query = "INSERT INTO large_table (id) VALUES ";
    for ($i = 0; $i < 10000; $i++) {
        $query .= "($i), ";
    }
    $query .= "($i)";
    $pdo->exec($query);
}

$result = $pdo->query("SELECT * FROM large_table");

foreach ($result as $i => $row)
    if ($i % 10000 === 0)
        printf("%10s %10s\n", $i, memory_get_usage());

I'm also getting a

Warning: Packets out of order. Expected 231 received 48. Packet size=3422212 in Unknown on line 0

after the memory limit error.


Previous Comments:
------------------------------------------------------------------------
[2018-12-28 21:06:31] cweiske@php.net

This breaks Roundcube webmail, see https://bugs.archlinux.org/task/61139.
Happens here with 7.3.0-2 (Debian 9)

------------------------------------------------------------------------
[2018-12-17 09:16:01] sjon at hortensius dot net

Description:
------------
commit f1f1f6 broke unbuffered queries in mysqlnd; there is a memory leak causing php to run out of
memory

Test script:
---------------
<?php
ini_set('memory_limit', '8M');

$pdo = new PDO('mysql:host=*;dbname=*', '*', '*');
$pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
$pdo->setAttribute(PDO::MYSQL_ATTR_USE_BUFFERED_QUERY, false);

$result = $pdo->query("SELECT * FROM large_table");

foreach ($result as $i => $row)
	if ($i % 10000 === 0)
		printf("%10s %10s\n", $i, memory_get_usage());


Expected result:
----------------
reasonable constant memory usage, eg:

         0     427648
     10000     427936
     20000     427968
     30000     427968
     40000     427936


Actual result:
--------------
         0     427296
     10000    2000288
     20000    3622336
     30000    5260736
     40000    6915488

Fatal error: Allowed memory size of 8388608 bytes exhausted (tried to allocate 16384 bytes) in /php
on line 10



------------------------------------------------------------------------



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Edit this bug report at https://bugs.php.net/bug.php?id=77308&edit=1

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