Using Filter with aggregation query builder

[fahimmahmoodmir]

Hi i am relatively new to ODM concepts with doctrine. I found there is no documentation updated for '$filter' array aggrgation filters. I am having trouble in returning only the matched embedded document using MongoDB ODM query builder in PHP. Each embedded document has a MongoID generated at the time of creation. Following is my document structure of collection Project:

{ 
    "_id" : ObjectId("59f889e46803fa3713454b5d"), 
    "projectName" : "usecase-updated", 
    "classes" : [
        {
            "_id" : ObjectId("59f9d7776803faea30b895dd"), 
            "className" : "OLA"
        }, 
        {
            "_id" : ObjectId("59f9d8ad6803fa4012b895df"), 
            "className" : "HELP"
        }, 
        {
            "_id" : ObjectId("59f9d9086803fa4112b895de"), 
            "className" : "DOC"
        }, 
        {
            "_id" : ObjectId("59f9d9186803fa4212b895de"), 
            "className" : "INVOC"
        }
    ]
}

Now i want to retrieve from the database only the class from the classes embedded documents which meets my criteria (i.e. class with a specific id).This is how i am building the query with simple query builder:

$qb = $dm->createQueryBuilder('Documents\Project');
$projectObj = $qb
    ->field('id')->equals("59f889e46803fa3713454b5d")
    ->field('classes')->elemMatch(
        $qb->expr()->field("id")->equals(new \MongoId("59f9d7776803faea30b895dd"))
    )
    ->hydrate(false)
    ->getQuery()
    ->getSingleResult();

First i match with the project id then i match with the embedded document class id. I was expecting it to return only the embedded document of OLA like this:

{ 
   "_id" : ObjectId("59f889e46803fa3713454b5d"), 
    "projectName" : "usecase-updated", 
    "classes" : [
          {
            "_id" : ObjectId("59f9d7776803faea30b895dd"), 
            "className" : "OLA"
          }
     ]
}

But doctrine is returning the whole Project record (shown in the start of question).I also tried with aggregation query building with the $match aggregation and $filter array operators of mongodb like this:

        $qb = $dm->createAggregationBuilder('Documents\Project');
        $projectObj = $qb
            ->match()
            ->field('id')->equals($projectId)
            ->field('classes._id')->equals(new \MongoId($classId))
            ->project()
            ->filter('classes', "class", array('class._id' => new \MongoId($classId)))
            ->execute();

But i am getting following exceptions:

MongoResultException\nCode: 16410\nMessage: localhost:27017: FieldPath field names may not start with '$'.\nFile: /var/www/html/doctor/lib/composer/vendor/doctrine/mongodb/lib/Doctrine/MongoDB/CommandCursor.php\nLine: 194\nTrace: #0 /var/www/html/doctor/lib/composer/vendor/doctrine/mongodb/lib/Doctrine/MongoDB/CommandCursor.php(194): MongoCommandCursor->rewind()\n#1 /var/www/html/doctor/lib/composer/vendor/doctrine/mongodb/lib/Doctrine/MongoDB/CommandCursor.php(257): Doctrine\\MongoDB\\CommandCursor->Doctrine\\MongoDB\\{closure}()\n#2 /var/www/html/doctor/lib/composer/vendor/doctrine/mongodb/lib/Doctrine/MongoDB/CommandCursor.php(195): Doctrine\\MongoDB\\CommandCursor->retry(Object(Closure))\n#3 /var/www/html/doctor/lib/composer/vendor/doctrine/mongodb-odm/lib/Doctrine/ODM/MongoDB/CommandCursor.php(191): Doctrine\\MongoDB\\CommandCursor->rewind()\n#4 /var/www/html/doctor/api/index.php(559):

I also tried adding a question on stackoverflow but not got any reply so far. Can anyone help me because i think i am using the wrong syntax for creating aggregation query builder but i am unable to find any example how to make it right.

[malarzm]

I see that SO question was answered so I'm closing this issue. If there's anything ODM could improve, please re-open :)