91bc0130fa
Summary: 1. refactor out PickFileToCompact to remove duplicated logic. 2. remove redundant checks of `start_level_inputs_.empty()`. Pull Request resolved: https://github.com/facebook/rocksdb/pull/6804 Test Plan: make check Reviewed By: siying Differential Revision: D21390053 Pulled By: cheng-chang fbshipit-source-id: 185d5987a08bfdaf63f0f245310c6da69878d415