Can't create foreign key using SCHEMA API

Question

I am trying to create 2 tables, linked together, using this code:

$schema['parent'] = array(
    "fields" => array(
        "id" => array(
            'description' => 'The primary identifier',
            'type' => 'serial',
            'unsigned' => TRUE,
            'not null' => TRUE,
        ),
        'data' => array(
            'description' => 'The stored data.',
            'type' => 'varchar',
            'length' => 255,
            'not null' => TRUE,
            'default' => '',
        ),
    ),
    'primary key' => array('id'),
);

$schema['child'] = array(
    // {{{fields

    "fields" => array(
        "id" => array(
            'description' => 'The primary identifier',
            'type' => 'serial',
            'unsigned' => TRUE,
            'not null' => TRUE,
        ),
        "parent_id" => array(
            'type' => 'int',
            'unsigned' => TRUE,
        ),
        'data' => array(
            'description' => 'The stored data.',
            'type' => 'varchar',
            'length' => 255,
            'not null' => TRUE,
            'default' => '',
        ),
    ),
    // }}}
    'indexes' => array(
        "parent_id" => array("parent_id"),
    ),
    'foreign keys' => array(
        'parent_id' => array(
            'table' => 'parent',
            'columns' => array('id' => 'parent_id'),
        ),
    ),
    'primary key' => array('id'),
);

foreach ($schema as $key => $value) {
    print $key . "\n";
    db_create_table($key, $value);
}

The tables are created, but the foreign keys are not. Using MySQL/InnoDB. How to fix it?

Also how to set ON DELETE CASCADE and ON UPDATE CASCADE?

Answer 1

Schema Reference

Foreign key definitions were added in Drupal 7 for documentation purposes only, and do not modify the database.