MySQL Bugs: #52234: mysql tries to allocate 4294967296 bytes when fetching longtext via php-mysqli

Bug #52234	mysql tries to allocate 4294967296 bytes when fetching longtext via php-mysqli
Submitted:	19 Mar 2010 20:28	Modified:	25 Mar 2010 7:09
Reporter:	Moritz Schönauer	Email Updates:
Status:	Not a Bug	Impact on me:	None
Category:	MySQL Server: Data Types	Severity:	S3 (Non-critical)
Version:	5.1.44	OS:	Linux (gentoo)
Assigned to:		CPU Architecture:	Any
Tags:	allocate, longtext, mysqli, php, prepared

Description:
I wanted to fetch some lines in a php script via mysqli-prepared-statement and got this error:
Allowed memory size of 134217728 bytes exhausted (tried to allocate 4294967296 bytes)
I was confused because php reportet that this error occured at bind_result.
After some time I figured out that it works when I turn one field with LONGTEXT type to VARCHAR, for example.

here is a link to my php-script:
http://paste.minad.de/?nid=216

How to repeat:
I can repeat this by fetching a LONGTEXT type field with a mysqli-prepared-statment.

Thank you for the report.

Please provide output of SHOW CREATE TABLE news and SELECT length(BLOB_FIELD) from news.

SHOW CREATE TABLE news
CREATE TABLE `news` ( `n_id` int(13) NOT NULL AUTO_INCREMENT, `n_title` varchar(50) NOT NULL, `n_note` longtext NOT NULL, `n_time` varchar(107) NOT NULL, `n_author` int(13) NOT NULL, PRIMARY KEY (`n_id`) ) ENGINE=MyISAM AUTO_INCREMENT=4 DEFAULT CHARSET=utf8

SELECT length(n_note) from news
5

Thank you for the feedback.

I can not repeat described behavior. Please also provide compete PHP code demonstrating the problem including code used to connect to the database and create statement.

<?php
class db {

private $db;

  function __construct() {
    require('#db.php');
    $this->db = new mysqli($host, $user, $pass, $database);
  }

  function __destruct() {
    if(is_object($this->db)) $this->db->close();
  }

  function news_read($limit = 0) {
    if($limit == 0) $qry = "SELECT * FROM news ORDER BY n_id DESC";
    else $qry = "SELECT * FROM news ORDER BY n_id DESC LIMIT $limit";
    $stmt = $this->db->prepare($qry);
    $stmt->execute();
    $stmt->bind_result($n_id,$n_title,$n_note,$n_time,$n_author);
    while($stmt->fetch()) {
      $news = array(id => $n_id, title => $n_title, note => $n_note, time => $n_time, author => $n_author);
      $array[] = $news;
    }
    return $array;
  }

}

$db = new db;
$db->news_read();

?>

maybe it is caused by php?
minad ~ # php --version
PHP 5.2.13-pl0-gentoo (cli) (built: Mar 22 2010 18:46:54)
Copyright (c) 1997-2010 The PHP Group
Zend Engine v2.2.0, Copyright (c) 1998-2010 Zend Technologies

Thank you for the feedback.

> maybe it is caused by php?

Yes, this can be the cause: still no error in my environment.

But this can be caused by specific MySQL settings too. Please send us your my.cnf content also.

http://paste.pocoo.org/show/193248/  <-- my.cnf

i tried reinstalling of php and mysql, too, but without success.

Thank you for the feedback.

Problem is PHP of version 5.2.13: I just tried and bug is repeatable as described. While with different version of PHP (5.3 from outdated development sources) bug is not repeatable. Please open bug in PHP bugs database.

thank you!