gistfile1.js

> db.a.save({_id:1, vals: {first:[1,2,3,], second:[1,2,3]}})
> db.a.find()
{ "_id" : 1, "vals" : { "first" : [ 1, 2, 3 ], "second" : [ 1, 2, 3 ] } }
> db.a.find({},{"vals.first":{$slice:2}})
{ "_id" : 1, "vals" : { "first" : [ 1, 2 ], "second" : [ 1, 2, 3 ] } }


//I would have expected this to work... might call that a bug.

> db.a.find({},{"vals.first":1, "vals.first":{$slice:2}})
{ "_id" : 1, "vals" : { "first" : [ 1, 2 ], "second" : [ 1, 2, 3 ] } }


> db.a.find({},{"vals":0, "vals.first":{$slice:2}})      
{ "_id" : 1, "vals" : { "first" : [ 1, 2 ] } }