Currently both facts and reports (and their log join) are deleted using dependent => :destroy

1. each value is deleted in a single SQL
2. each AR object is initiated.

possible solutions:

• use dependent => :destroy_all which would fix 2
• use delete_all to delete all id's in a single query (one for facts, one for reports and another for logs).

since we are not doing any auditing on facts currently, it might be save enough to use delete_all (and remove about 70% of the time it takes to delete a host).