Exclude results from Lithium find

Question

I'd like to exclude results from a call to a Lithium model's find() method. I need to do this for models with both MongoDB and MySQL data sources, but in SQL I mean something like WHERE myfield NOT IN (1,2,3).

I'd like to just be able to pass a not clause in the conditions array like below, but that doesn't appear to be possible.

Item::all(array('conditions' => array('not' => array('myfield' => array(1,2,3))));

So my question is, is this possible in Lithium in a way that I've overlooked? And if not, what would be the most Lithium-ish way to implement it for my models?

Answer 1

Merely filtering for MongoDB can easily be achieved like this:

Item::all(array('conditions' =>                                                                                                                                                                                
    array('myfield' => array(                                                                                                                                                                                  
        '$nin' => array(1,2,3)                                                                                                                                                                                 
    ))                                                                                                                                                                                                         
));                                                                                                                                                                                                            

If this is something you do a lot you could even create a custom finder for it :

class MyModel extends \lithium\data\Model {                                                                                                                                                                    
    public static function __init()                                                                                                                                                                            
    {                                                                                                                                                                                                          
        parent::__init();                                                                                                                                                                                      

        static::finder('notin', function($self, $params, $chain) {                                                                                                                                             
            // Take all array keys that are not option keys
            $array = array_diff_key($params['options'],
                array_fill_keys(array('conditions', 'fields','order','limit','page'),0));
            // Clean up options leaving only what li3 expects
            $params['options'] = array_diff_key($params['options'], $array);
            $params['options']['conditions'] = array(
                'myfield' => array(
                    '$nin' => $array
                )
            );

            return $chain->next($self, $params, $chain);                                                                                                                                                       
        });                                                                                                                                                                                                    
    }                                                                                                                                                                                                          
}                                                                                                                                                                                                              

And call it like this :

MyModel::notin(array(1,2,3));                                                                                                                                                                                  

In the same manner you could create a custom finder for MySQL sources.

As you probably can see this creates some issues if you pass something like array('fields'=>$array) as it would overwrite the option. What happens is that ::notin() (finders in general) has a distinct behavior for the (array,null) signature. If that happens it thinks the first array is options and the finder took no arguments. Using notin($array,array()) breaks the previous finder because the first argument ends up in $params['notin'] when the real second argument (options) is passed.

If you mix data sources on the fly here I would create a custom model that does not inherit \lithium\data\Model and have it delegate
to the different models and create the conditions based on the end models data source.

class MyFacadeModel {                                                                                                                                                                                          
    public static function byNotIn($conditions, $source) {                                                                                                                                                     
        return ($source == "mongodb")                                                                                                                                                                          
            ? $source::find( $rewrittenConditions)                                                                                                                                                             
            : $source::find( $rewrittenConditionsForMysql );                                                                                                                                                   
    }                                                                                                                                                                                                          
}

(Code might be slightly incorrect as its mostly taken from the top of my head)

Answer 2

Just to clarify, Lithium's MongoDB adapter supports most SQL comparison operators as a convenience, so for either Mongo or MySQL, you could simply write the query as follows:

Item::all(array('conditions' => array(
    'myfield' => array('!=' => array(1,2,3))                                                                                                                                                                                 
)));

And it should give you the results you expect. For MySQL, the query should look something like:

SELECT * FROM items WHERE myfield NOT IN (1, 2, 3);

And in Mongo:

db.items.find({ myfield: { $nin: [1, 2, 3] }})