MongoDB filter array element in a nested object

Question

I have a document as follows:

{
    "_id" : ObjectId("56423b2558cb340599108b35"),
    "test" : {
        "source" : [
            {
                "member" : "abc"
            },
            {
                "member" : "xyz"
            }
        ]
    }
}

I want to filter on the array element xyz, and I am trying the following query:

db.coll.find({ "test.source.member" : "xyz" }, { "test.source.$.member" : true }).pretty()

Apparently it used to work on 2.4, on 2.6 it does not work,

On 2.4 it returned the "xyz", whereas on 2.6 it returns "abc" i.e. the first element. Is there a way to filter "abc" because eventually i want to update. BTW, i also tried with $elemMatch and it seems to give the same output "abc".

Thanks.

Answer 1

According to the Docs, if you are running 2.6, this should give you the correct output:

db.coll.find({ "test.source.member" : "xyz"}, { "test.source.$" : 1}).pretty()

You could extract the member by doing this:

var member = db.coll.find(
                 { "test.source.member" : "xyz"},
                 { "test.source.$" : 1}
                 ).test.source[0].member;

The value of member would be:

xyz