DBJ: a dynamic balancing hash join algorithm in multiprocessor database systems

The Dynamic Balancing Hash Join (DBJ), has been proposed to handle the problem of skewed data in the join operation in multiprocessor database systems. The objective of this new algorithm is to avoid the high cost of preprocessing inherent in existing algorithms. The new algorithm only redistributes a small portion of the partitioned data and, thereby achieves a balanced output with little extra cost. This is achieved dynamically, without knowledge of the input distribution, nor any co-ordinating processor. A performance analysis shows that the new algorithm performs better than existing balancing hash join algorithms for a wide degree of skew