Efficient range query retrieval for non-uniform data distributions

Answering range queries is a common database operation. Methods based on hashing techniques to minimise the cost of answering range queries by taking the query distribution into account have previously been proposed. These methods have all assumed a uniform distribution of data to disk pages to achieve good performance. This assumption makes them less useful in practice because most real data distributions are non-uniform. In this paper, we discuss a method to eliminate this restriction. Extensive experimentation using a multi-dimensional file structure, the BANG file, indicates that our method results in good performance for all data distributions. In one case an improvement of over 36 times was achieved without compromising the storage utilisation. Our method also results in a stable and efficient file organisation. If the query distribution does not change substantially, an optimised file organisation rarely requires reorganisation.