Hi. Here're I'll be asking questions about the patches I'm looking at. 1. Is this mostly a merge of WL#7305 or mostly your own implementation? That is, most of the changes and design decisions are yours or "because MySQL did it"? 2. Do you work like I do (commit, push, fix failing tests, combine commits with "git rebase -i" to get a clean history) or you've just magically got 32bit rdiffs correctly in every commit? :) 3. Why "MDL objects cache won't be needed"? The comment said "On some systems (e.g. Windows XP) constructing/destructing MDL_lock objects can be fairly expensive. We use this cache to avoid these costs..." Why is this no longer an issue? 4. MDL_lock_strategy - this object is in 5.7 too, but you've done it very differently. Why? And I wonder why didn't you move the common part of two strategies to the base class. You wanted a pure interface class? 5. Added initializer callback to lf-hash. May be you should remove this hack with decreasing LF_HASH::element_size etc and move this functionality to a custom initializer? It was added in 6ba12f. In particular, see changes to lf* files and whether they can use your initializer instead. 6. Replaced hash with lock-free hash: test result changes. Is the order of rows stable? perhaps you should use --sort_results ? in MDL_lock constructor, I'd set m_strategy to 0 (ori to 1 or, may be, keep it uninitialized) as a safety measure, to ensure it's not used before MDL_lock::lf_hash_initializer(). Otherwise looks ok. Mostly a straightforward change. Regards, Sergei