T-tree or B-tree: main memory database index structure revisited

While the B-tree (or the B/sup +/-tree) is the most popular index structure in disk-based relational database systems, the T-tree has been widely accepted as a promising index structure for main memory databases where the entire database (or most of them) resides in the main memory. However, most work on the T-tree reported in the literature did not take concurrency control into consideration. In this paper we report our study on the performance of the main memory database index structure that allows concurrent accesses of multiple users. Two concurrency control approaches over the T-tree are presented. The results of a simulation study indicate that the B-link tree, a variant of the widely used B-tree index will outperform the T-tree if concurrency control is enforced. This is due to the fact that concurrency control over a T-tree requires more lock operations than that of a B-link tree, and the overhead of locking and unlocking is high.