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2.1.9 Root Block protocol

Root uniqueness

We guarantee that the root block number never changes and thus can be used as a unique identifier for a given WB-tree. Other systems provide a unique tree ID by introducing a level of indirection in root references; this is inefficient, as root references are frequent. When the root is split, we allocate a new block to hold the data that would have remained in the root block, then use the old root block for the new root. This does mean that one cannot depend on a block’s ID being unchanged if it splits!

ROOT DELETE and Reducing number of levels in a tree