PHP 5.3.5 PDO FETCH_OBJ内存泄漏？

Question

I'm currently developing an application in PHP which uses PDO. I'm writing an import which reads in a CSV file, checks the database for a record, and updates, deletes, etc....

Something which I've noticed is the memory being used by this script seems very high and it seems like it could be to do with the way I'm executing the query. see below for example query which is executed for each line in the CSV:

$qry = "SELECT * FROM company WHERE id = 1";
$sth = $this->prepare($qry);
$sth->execute();
$sth->setFetchMode(PDO::FETCH_INTO, new Company());
$sth->fetch();

for the above memory_get_peak_usage() = 6291456

When using the below:

$qry = "SELECT * FROM company WHERE id = 1";
$sth = $this->prepare($qry);
$sth->execute();
$sth->setFetchMode(PDO::FETCH_CLASS, "Company");
$sth->fetch();

for the above memory_get_peak_usage() = 524288

As you can see the difference is fairly big.

I guess I've 3 questions..

1. Is there a memory leak when using PDO::FETCH_OBJ in PHP 5.3.5?
2. Is there any difference between using FETCH_CLASS as opposed to FETCH_OBJ?
3. Has anyone else experienced the same issue?

Company Class is simple:

class Company {
    function __construct(){}
    /**classvars**/
    public $_tablename = 'company';
    public $transient;
    public $id;
    public $name;
    /**endclassvars**/
} 

Answer 1

Looking at the PHP changelog , there does appear to be a relevant fix in 5.3.4 where a memory leak was fixed in PDO FETCH_INTO .

From what you've said, I suspect that yes, this is the bug you're seeing. The solution, of course, is to upgrade -- there really is no point in sticking with an old patch release.

Even if this isn't the bug you're seeing, there have been a very large number of PDO fixes in the versions between 5.3.3 and now; I'm sure there's a good chance that at least some of them are relevant to you.

Answer 2

Note : the original answer was given before the OP changed PDO::FETCH_OBJ to PDO::FETCH_INTO

After that update I've tried to reproduce the behaviour using PHP 5.3.10-1ubuntu3.4 . There where no significant difference in memory cosumption between both fetch modes. I've tested using a large MySQL table and a large SQLite database.

As @SDC mentioned the bug is known and was fixed after 5.3.5. (At least in 5.3.10 as I've seen).

Conclusion: You have to upgrade your PHP version.

---

Although the behaviour is interesting and should be investigated you are using PDO::setFetchMode() in a wrong way. When $mode - the first param - is PDO::FETCH_OBJ no second param is expected. If you use a second param the call to setFetchMode() will fail (returnin false) and the default fetch mode FETCH_BOTH will be used.

You can see this error when enabling PDO::ERRMODE_EXCEPTION :

$db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

$stmt = $db->query('....');

// the following line will trigger an exception
$stmt->setFetchMode(PDO::FETCH_OBJ, new Company());

Fatal error: Uncaught exception 'PDOException' with message 'SQLSTATE[HY000]: General error: fetch mode doesn't allow any extra arguments'

When you are expecting that result rows should objects of a specific class, then PDO::FETCH_CLASS is the working attempt. PDO::FETCH_OBJ will return objects from type StdClass

Answer 3

FETCH_INTO: Means fetching into an existing Object (that was created with new eg)

FETCH_CLASS: Means fetching into an new Object (the constructor is called every row)

Be careful, if the constructor in your Company class has dependencies, they are called for every row. Therefore the constructor should not contain functions or classes that do an DB connect eg only simple initializing...

How does your Company class look like?