How to create Index to find null values of fields(myField:null)?

I have order collection with many fields. When I run allOrders index(list of all orders) with some fields I get following result.

Now I want to find how many orders are there with null value of myField, so I am creating index

   name: "findbyMyField",
   source: Collection("Order"),
     terms: [
    { field: ["data", "myField"]}

but above index doesnot return any data when called by

q.Paginate(q.Match(q.Index("findbyMyField"), null))

How to get documents with null values of given field?

Use Index binding.