Within get_runs and get_caseruns method in build.py, build is the necessary criteria to search all objects associated with the TestBuild. Both of these twos get a real TestBuild object and then construct search criterias object, which is a django QuerySet criterias.

However, according to the ability of django's ORM, it's unnecessary to pass a complete TestBuild object, only the ``build_id`` is enough. Thus, one SQL query consumption is saved, and we can imagine how much resources can be saved in the server side, when those two method is being used in auto testing scripts.