Summary:
Right now there is no support for enabling compaction filter in db_bench, we should add support for that to facilitate testing of compaction filter.
This PR adds a compaction filter called KeepFilter and make `Filter` always returns false, essentially a noop compaction filter. This will allow us to test compaction filter code path without having to support arbitrary compaction filters
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4106
Differential Revision: D8828517
Pulled By: miasantreble
fbshipit-source-id: 9ad76d04103eaa9d00da98334b4a39e542d26c41
de98fd88e3