CakePHP hasOne ineffeciency?

Question

I was looking at examples on the CakePHP website, in particular hasOne used in linking models. http://book.cakephp.org/view/78/Associations-Linking-Models-Together

My question is this, is CakePHP using two queries to build the array structure of data returned in a model that uses hasOne linkage?

Taken from CakePHP: //Sample results from a $this->User->find() call.

Array
(
    [User] => Array
        (
            [id] => 121
            [name] => Gwoo the Kungwoo
            [created] => 2007-05-01 10:31:01
        )
    [Profile] => Array
        (
            [id] => 12
            [user_id] => 121
            [skill] => Baking Cakes
            [created] => 2007-05-01 10:31:01
        )
)

Hope this all makes sense.

Answer 1

pretty sure most if not all hasOne and belongsTo are done using join. so one query. you can always set debug to 2 in config.php to see the sql query

Answer 2

Model::find uses joins to retrieve model records associated to the source model by hasOne and belongsTo relationships. The specific SQL queries look something like (using a Car belongsTo Driver model structure):

SELECT `Car`.`brand`, `Car`.`colour`, `Driver`.`name`, `Driver`.`age`
    FROM `cars` AS `Car`
    LEFT JOIN `drivers` AS `Driver` ON `Car`.`id` = `Driver`.`car_id`
WHERE `Car`.`brand` = 'Aston Martin'

The fields belonging to each model can be parsed out into corresponding array elements by the table/model alias:

• Car.brand becomes $result['Car']['brand']
• Car.colour becomes $result['Car']['colour']
• Driver.name becomes $result['Driver']['name']
• Driver.age becomes $result['Driver']['age']

Only one query required.

Retrieving data for hasMany and hasAndBelongsToMany associations requires additional queries, sometimes many more.