Abstract: Data stream query processing technology becomes a new and popular topic in database research area.The critical of improving non-blocking join algorithm is to improve the efficiency of memory join stage. If there are no more space for the coming tuple, some old tuples have to be flushed from memory to disk. A good refresh strategy is very helpful to increase join algorithm performance. The lowest frequently used tuples are searched from the result streams, then flush such tuples from memory to disk so that the tuples that arc stayed in the memory would generate more results. Statistics join algorithm performance is increased obviously and it expands the adaptability of the data stream relation join algorithm.

Key words: Data stream,Non-blocking join,Memory flush strategy