Fast SQLAlchemy counting (avoid query.count() subquery)

gistfile1.py

def get_count(q):
    count_q = q.statement.with_only_columns([func.count()]).order_by(None)
    count = q.session.execute(count_q).scalar()
    return count

q = session.query(TestModel).filter(...).order_by(...)

# Slow: SELECT COUNT(*) FROM (SELECT ... FROM TestModel WHERE ...) ...
print q.count()

# Fast: SELECT COUNT(*) FROM TestModel WHERE ...
print get_count(q)

This is the method, I'm using

def get_count(self, model_fields, filter_clause):
        """ Note: filter_clause should not be 'None' or 'Null' for this method to work """
        query = self.session.query().with_entities(*model_fields)
        query = query.filter(filter_clause)
        count_query = query.statement \
                .with_only_columns([func.count()]) \
                .order_by(None)
        result = query.session.execute(count_query).scalar()
        return result