Summary:
This PR associates a unique id with Get and MultiGet. This enables us to track how many blocks a Get/MultiGet request accesses. We can also measure the impact of row cache vs block cache.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5514
Test Plan: make clean && COMPILE_WITH_ASAN=1 make check -j32
Differential Revision: D16032681
Pulled By: HaoyuHuang
fbshipit-source-id: 775b05f4440badd58de6667e3ec9f4fc87a0af4c