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• Add support for MVCC (TRANSACTIONAL_SNAPSHOT) cache mode.

Risks and Assumptions

1. In-memory eviction policy can be configured in such a way that will lead to OOM when using batch writing to data pages, so in some degenerate cases the batch writing must be disabled.
2. For BPlusTree batch operations, ordered keys are required, moreover, an attempt to simultaneously lock the same keys in a different order lead to a deadlock, so batch insertion into the page memory must be performed on an unlocked entries. Alternatively, keys passed in batches from different components (preloader, datastreamer, putAll) should be locked in the same order.
3. Heap usage/GC pressure.

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