Indexing Multiple Sets

Index structures for multiple sets can be classified into those that group entries according to their key values and those that group entries according to their set membership. The former are particularly suited for exact match queries on all indexed sets, the latter especially support range queries on a small number of all indexed sets. The goal is to thoroughly evaluate the performance of both grouping strategies. There exist two reasons for adding a new index structure to the evaluation: (1) The performance potentials of set grouping index structures are not yet fully exploited. (2) Up to now, the database administrator has to choose between key grouping an l-l set grouping index structures, supporting eit er exact match or range queries. What is needed is a more flexible index structure that can be tuned to a given query mix containing both, exact match and range queries. These two reasons led us to the development of the CG-tree. The focus of the paper is on introducing the CG-tree and on a thorough performance analysis of the CH-index [7’J, the H-tree [8, 91 and the CGtree.