How to export millions of rows from MySQL to CSV via PHP without running out of memory?

Question

So, I have this table:

mysql> DESCRIBE table;
+-------+------------------+------+-----+---------+----------------+
| Field | Type             | Null | Key | Default | Extra          |
+-------+------------------+------+-----+---------+----------------+
| id    | int(15) unsigned | NO   | PRI | NULL    | auto_increment |
| unid  | char(9)          | NO   | UNI | NULL    |                |
| rs    | varchar(255)     | NO   |     | NULL    |                |
+-------+------------------+------+-----+---------+----------------+
3 rows in set (0.00 sec)

Which contains millions of lines:

mysql> SELECT COUNT(1) FROM table;
+----------+
| COUNT(1) |
+----------+
|  9435361 |
+----------+
1 row in set (0.00 sec)

I want to export all lines to a file .csv(I use Symfony2.6). This file is intended for storage on the server (not loaded), and then, read by PHP.

First try

I tried to make a huge request to select everything at once ( in accordance with this blog post ), but this, despite the use ->iterate(), led to Allowed memory size of 1073741824 bytes exhausted~ 9 s after a run.

    ini_set('memory_limit', '1024M');
    ini_set('max_execution_time', -1);

    $results = $em
        ->getRepository('MyBundle:Entity')
        ->createQueryBuilder('e')
        ->getQuery()
        ->iterate();
    $handle = fopen('/path/to/csv/file/', 'w');
    while (false !== ($row = $results->next())) {
        fputcsv($handle, $row[0]->toArray());
        $em->detach($row[0]);
    }
    fclose($handle);

Second attempt

, , . , ~ 260 . .csv, PHP , : Allowed memory size of 1073741824 bytes exhausted.

    ini_set('memory_limit', '1024M');
    ini_set('max_execution_time', -1);

    $total = (int) $em
        ->getRepository('MyBundle:Entity')
        ->countAll();
    $csv = '/path/to/csv/file';
    $handle = fopen($csv, 'w');
    for($i = 1; $i < $total; $i++)
    {
        $entity = $em->getRepository('MyBundle:Entity')->findOneById($i);
        fputcsv($handle, $entity->toArray());
        $em->detach($entity);
    }
    fclose($handle);

exec() MySQL, . , , .

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, , ~ 9.5M PHP .csv ? , ?

.

Answer 1

, -, : http://dev.mysql.com/doc/refman/5.7/en/select.html

-

SELECT * INTO OUTFILE "c:/temp/mycsv.csv"
FIELDS TERMINATED BY ',' OPTIONALLY ENCLOSED BY '"'
LINES TERMINATED BY "\n"
FROM theTable;

mysql php.

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venca: , mysql, .