关键词: 数据流, 滑动窗口, 聚集查询, 共享, 链树, 跳数

Abstract: How to improve the efficiency of multi-aggregate queries is a key problem, to which a novel linked-tree sharing strategy is proposed to support multi-aggregate queries in sliding window over data streams. In this way, each and every sliding window will divide the linked-tree logically into several sub-trees where the aggregate values of different root nodes are just the answers corresponding to their aggregate queries. This kind of logical division makes several queries run in a tree simultaneously, thus avoiding the repeated construction of different linked-trees. Taking advantage of the characteristic of the linked-tree available to reduce the number of fruitlessly repeated comparisons, the aggregate value of each query can be given with few updates/comparisons to do when many queries are required for answers from the same linked-tree. Extensive experiments showed that sharing the same linked-tree can cause lots of queries to share the resources with memory content decreased accordingly. As a result, the query processing efficiency, throughputs of real time tasks and system's performance are all improved dramatically.