Lithium mongodb relation between models - mongodb

Question

I'm using lithium with mongodb and I would like to know with my models below how I could get the data of the user from Posts::find('all'); query?
Do I have to do two queries?
Thanks for your help!
<?php
namespace app\models;
class Posts extends \lithium\data\Model {
protected $_schema = array(
'_id' => array('type' => 'id'),
'name' => array('type' => 'string', 'null' => false),
'description' => array('type' => 'string', 'null' => false),
'created' => array('type' => 'datetime'),
'updated' => array('type' => 'datetime'),
'user_id' => array('type' => 'integer')
);
protected $_meta = array(
'key' => '_id',
);
public $belongsTo = array('Users');
}
?>
<?php
namespace app\models;
class Users extends \lithium\data\Model {
public $hasMany = array('Posts');
public $validates = array(
'name' => 'Please enter a name',
);
protected $_schema = array(
'_id' => array('type' => 'id'),
'name' => array('type' => 'string', 'null' => false),
'slug' => array('type' => 'string', 'null' => false),
'created' => array('type' => 'datetime', 'null' => false),
);
}
?>

Answer 1

Currently relationships only exist for relational databases like MySQL and SQLite3. As such you'll need to make two queries to get the data you want. We're working on adding support for relationships for document based databases now however there currently is no timeframe on that.
You can use Set::extract on your result from posts to pull all of the user id's out then use the results from that to make a single query from users - so from posts you could do $userIDs = Set::extract('/posts/user_id', $posts->data()); then User::find('all', array('conditions' => array('_id' => $userIDs)));
hope this helps.
edit: You can find set::extract information here: http://li3.me/docs/lithium/util/Set::extract()

Answer 2

Do I have to do two queries?
This will depend on your schema.
Case #1
If Users and Posts are two different collections then you will need two different queries.
Case #2
If Users is the top level object and Posts "belongs to" Users then you would do something equivalent to db.users.find({ posts : {$exists:true} }).
I'm not 100% clear on how Lithium handles this. I cannot find a simple example of whether Lithium is doing #1 or #2.

Answer 3

As Howard3 said, there is currently no relationship support for MongoDB and as a result "belongs to" won't work either.
The actual decision depends on your application, but i assume that its going to be some form of a blog (users and posts). According to MongoDB schema design best practices, i'd put both in separate collections because they are "first level collections". a better fit for embedded documents would be posts and comments.
Also, you don't have to define the 'key' stuff when you're on latest master. You can write a custom find method for now that could be easily swapped to the more generic solution when relation support is finished in the core.
if you need more interactive help, visit #li3 on freenode.