TokuDB underlying storage structure of Fractal Tree . Fractal Tree B + tree structure and have similar, but in addition each of the Fractal Tree pointer key, requires a point to point child node, a child node with Message Buffer, the Message Buffer is a FIFO queue, it is used to cache update operation, specific data structures shown in FIG.
In this way, every time you insert operations are just landed on the Message Buffer certain node, you can return immediately and do not need to search to the leaf node. The cache update operation in the background were combined asynchronous and updates to the corresponding nodes.
Add TokuDB online index does not affect the read and write operations, there is a very high write performance, mainly for applications that require fast write speed, access frequency is not high or historical data archiving.
