Major Description
A view without its base table is an orphan view. Since views are virtual tables and their data is stored in their base tables, they are useless when they become orphan. A base table can have child views, grandchild views and so on. Due to some reasons/bugs, when a base table was dropped, its views were not not properly cleaned up in the past. For example, the drop table code did not support cleaning up grandchild views. This has been recently fixed by PHOENIX-4764. Although PHOENIX-4764 prevents new orphan views due to table drop operations, it does not clean up existing orphan views. It is also believed that when the system catalog table was split due to a bug in the past, it also contributed to creating orphan views as Phoenix did not support splittable system catalog. Therefore, Phoenix needs a tool to clean up orphan views.
