Fractal tree indexes also have several performance optimizations. First, buffers are themselves indexed in order to speed up searches. Second, leaves are much larger than in B-trees, which allows for greater compression. In fact, the leaves are chosen to be large enough that their access time is dominated by the bandwidth time, and therefore amortizes away the seek and rotational latency. Large leaves are an advantage with large range queries but slow down point queries, which require accessing a small portion of the leaf. The solution implemented in fractal tree indexes is to have large leaves that can be fetched as a whole for fast range queries but are broken into smaller pieces call basement nodes which can be fetched individually. Accessing a basement node is faster than accessing a leaf, because of the reduced bandwidth time. Thus the substructure of leaves in fractal tree indexes, as compared to Bε trees allows both range and point queries to be fast.
