In this paper, an effective index structure for dynamic main memory database systems, which we call the T2-tree, is presented. A notion of a thread pointer is introduced to overcome some of the limitations of the T-tree and the T*-tree. There are several advantages to this structure. First, the T2-tree reduces the number of rotate operations and the overhead required for balancing the tree by restraining new node creation and deletion. Second, the T2-tree shows good performance for sequential search of range queries as these requests can be effectively handled using the successor pointer. Finally, the T2-tree allows for higher space utilization amplicating the aforementioned benefits. These advantages are obtained with minimal changes to the existing T-tree structure. Experimental studies showing evidence of the benefits of the T2-tree are also presented.

Efficient query processing in multi-dimensional indexing structures is an important issue for multimedia data applications. In this paper, we propose incremental k-nearest neighbor query (k-NNQ) and range query algorithms for R-tree based structures. The novel aspect of these algorithms is that they make use of the notion of VP filtering, a concept borrowed from the MVP-tree. The filtering notion allows for delaying of computational overhead until absolutely necessary. By so doing, we attain considerable performance benefits while paying insignificant overhead during the construction of the index structure. We implemented our algorithms and carried out experiments to demonstrate the capability and usefulness of our method. Results show that improvements range from 8% to 23% in response time for the experimental environment that we considered.