I recently started using MongoDB and I have a question regarding updating arrays in a document.
I got structure like this:

```
{
"_id" : ObjectId(),
"post" : "",
"comments" : [
        {
                "user" : "test",
                "avatar" : "/static/avatars/asd.jpg",
                "text" : "....."
        }
        {
                "user" : "test",
                "avatar" : "/static/avatars/asd.jpg",
                "text" : "....."
        }
        {
                "user" : "test",
                "avatar" : "/static/avatars/asd.jpg",
                "text" : "....."
        }
        ...
   ]
}

```

I'm trying to execute the following query:

```
update({"comments.user":"test"},{$set:{"comments.$.avatar": "new_avatar.jpg"}},false,true)

```

The problem is that it update all documents, but it update only the first array element in every document. Is there any way to update all array elements or I should try to do it manually?
Thanks.