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c9ce4a3d6b
Summary: Motivated by code review issue in https://github.com/facebook/rocksdb/issues/13316, we don't want to release the DB mutex in SetOptions between updating the cfd latest options and installing the new Version and SuperVersion. SetOptions uses LogAndApply to install a new Version but this currently incurs an unnecessary manifest write. (This is not a big performance concern because SetOptions dumps a new OPTIONS file, which is much larger than the redundant manifest update.) Since we don't want IO while holding the DB mutex, we need to get rid of the manifest write, and that's what this change does. We introduce a kind of dummy VersionEdit that allows the existing code paths of LogAndApply to install a new Version (with the updated mutable options), recompute resulting compaction scores etc., but without the manifest write. Part of the validation for this is new assertions in SetOptions verifying the consistency of the various copies of MutableCFOptions. (I'm not convinced we need it in SuperVersion in addition to Version, but that's not for here and now.) These checks depend on defaulted `operator==` so depend on C++20. Pull Request resolved: https://github.com/facebook/rocksdb/pull/13384 Test Plan: New unit test in addition to new assertions. SetOptions already tested heavily in crash test. Used `ROCKSDB_CXX_STANDARD=c++20 make -j100 check` to ensure the new assertions are verified Reviewed By: cbi42 Differential Revision: D69408829 Pulled By: pdillinger fbshipit-source-id: 4cf026010c6bb381e0ea27567cce2708d4678e7d