Getting a distinct aggregation of an array field across indexes

Question

I\'m trying to learn MongoDB and how it\'d be useful for analytics for me. I\'m simply playing around with the JavaScript console available on their website and have created

Answer 1

You can use the aggregation framework. Depending on how you'd like the results structured, you can use either

var pipeline = [ 
        {"$unwind": "$tags" } ,
        { "$group": { _id: "$tags" } }
    ];
R = db.tb.aggregate( pipeline );
printjson(R);

{
        "result" : [
                {
                        "_id" : "seventy"
                },
                {
                        "_id" : "ten"
                },
                {
                        "_id" : "sixty"
                },
                {
                        "_id" : "thirty"
                },
                {
                        "_id" : "twenty"
                }
        ],
        "ok" : 1
}

or

var pipeline = [ 
        {"$unwind": "$tags" } ,
        { "$group": 
            { _id: null, tags: {"$addToSet": "$tags" }  }
        }
    ];
R = db.tb.aggregate( pipeline );
printjson(R);

{
        "result" : [
                {
                        "_id" : null,
                        "tags" : [
                                "seventy",
                                "ten",
                                "sixty",
                                "thirty",
                                "twenty"
                        ]
                }
        ],
        "ok" : 1
}