> db.foo.find()

{ "_id" : ObjectId("4b1fd7257a88ded6296525ba"), "k" : 3 }

> db.foo.find(

{ "_id" : ObjectId("4b1fd7257a88ded6296525ba")}

)

{ "_id" : ObjectId("4b1fd7257a88ded6296525ba"), "k" : 3 }

> db.foo.find(

{ "_id" : ObjectId("4b1fd7257a88ded6296525ba")}

).explain()

{ "_id" : ObjectId("4b1fd7257a88ded6296525ba"), "k" : 3 }