I am trying to execute a query on nova db in a custom code file in nova. During the execution of 

a function like 'instance_get_all_by_filters_sort'  from nova/db/main/api.py ,  I see this 

--- 

 try:
        query_prefix = sqlalchemyutils.paginate_query(
            query_prefix,
            models.Instance,
            limit,
            sort_keys,
            marker=marker,
            sort_dirs=sort_dirs,
        )
    except db_exc.InvalidSortKey:
        raise exception.InvalidSortKey()

    instances = query_prefix.all()

---

So, my question is how does query_prefix.all() know the mysql db connection url to connect to for executing the query ?

Thanks

elinux