> db.test.save( { _id : 1 , a : [

{ x : 1 , y : 2 }

,

{ x : 10 , y : 11 }

] })
> db.test.find()
{ "_id" : 1, "a" : [

{ "x" : 1, "y" : 2 }

,

{ "x" : 10, "y" : 11 }

] }
> db.test.update( {}, { $unset:

{"a.0":1}

} )
> db.test.find()

{ "_id" : 1, "a" : [ null ] }

Expected { "_id" : 1, "a" : [

{ "x" : 10, "y" : 11 }

] }

$unset on the 1st idx (2nd element) works fine though.