gistfile1.js

> db.test0.find({v:{$all:[1,2]}})
{ "_id" : 2, "v" : [ 1, 2, 3 ] }
> db.test0.find({v:{$all:[1,2]}}).explain()
{
        "cursor" : "BasicCursor",
        "nscanned" : 3,
        "nscannedObjects" : 3,
        "n" : 1,
        "millis" : 37,
        "nYields" : 0,
        "nChunkSkips" : 0,
        "indexBounds" : {

        }
}
> db.test0.ensureIndex({v:1})
> db.test0.find({v:{$all:[1,2]}}).explain()
{
        "cursor" : "BtreeCursor v_1",
        "nscanned" : 1,
        "nscannedObjects" : 1,
        "n" : 1,
        "millis" : 0,
        "nYields" : 0,
        "nChunkSkips" : 0,
        "indexBounds" : {
                "v" : [
                        [
                                1,
                                1
                        ]
                ]
        }
}