Here is my streaming wrapper for `es_query` https://github.com/dimagi/commcare-hq/blob/master/corehq/elastic.py#L266. However this assumes that you're gonna be using `es_query` to handle your elasticsearch querying. However, it seems like this report using does it's querying by leveraging `CaseES` which subclasses Dan's ESView (a class based view for querying elasticsearch.) You would probably have to modify the `run_query` fn in that class to support streaming requests.