Find matching array items in MongoDB document - codeigniter

Question

I am developing a web app using Codeigniter and MongoDB.
In the database I got a document that look like this:
{
"_id": {
"$id": "4f609932615a935c18r000000"
},
"basic": {
"name": "The project"
},
"members": [
{
"user_name": "john",
"role": "user",
"created_at": {
"sec": 1331730738,
"usec": 810000
}
},
{
"user_name": "markus",
"role": "user",
"created_at": {
"sec": 1331730738,
"usec": 810000
}
}
]
}
I need to search this document using both user_name and role. Right now when I am using the below code I get both. I only want to get array items matching both user_name and role.
$where = array (
'_id' => new MongoId ($account_id),
'members.user_id' => new MongoId ($user_id),
'members.role' => $role
);
$this -> cimongo -> where ($where) -> count_all_results ('accounts');

Answer 1

This is an old question, but as of MongoDB 2.2 or so you can use the $ positional operator in a projection so that only the matched array element is included in the result.
So you can do something like this:
$this->cimongo->where($where)->select(array('members.$'))->get('accounts');

Answer 2

This is a repeat of this question:
Get particular element from mongoDB array
Also you might want to use $elemMatch
http://www.mongodb.org/display/DOCS/Advanced+Queries#AdvancedQueries-ValueinanArray
Here is the rub -- you aren't going to be able to get the array items that match because mongo is going to return the entire document if those elements match. You will have to parse out the code client side. Mongo doesn't have a way to answer, "return only the array that matches."