Better materialized views update #86
Description
Currently, every "commit" into DB (aka SetActiveVersion) drops and recreates materialized views. Maybe we can use refresh in some cases instead.
I think this task should have low priority as metadata isn't that big and materialized views creation is fast enough. Also, https://github.com/src-d/applications-backlog/issues/13 will affect the solution.