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What can you achieve by implementing reverse key index?
A.Reverse the bytes of each column indexed including the row ID.
B.Store a bitmap for each key value instead of a list of row IDs in the leaf node.
C.Prevent contention on the highest leaf block when using sequences to generate keys.
D.Remove repeated key values from the index to fit more index entries in a given amount of disk space.

A 改变的是字符顺序，不是列顺序
B 描述的是 bitmap index
C 正确
D Remove repeated key values 可以尝试用函数索引 substr()达到