Summary:
Recently, a bug was found related to a seek key that is close to SST file boundary. However, it only occurs in a very small chance in db_stress, because the chance that a random key hits SST file boundaries is small. To boost the chance, with 1/16 chance, we pick keys that are close to SST file boundaries.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6037
Test Plan: Did some manual printing out, and hack to cover the key generation logic to be correct.
Differential Revision: D18598476
fbshipit-source-id: 13b76687d106c5be4e3e02a0c77fa5578105a071