Data Stream Query Operator Algorithm

With the fast development of computer application, nowdays data stream processing is becoming the new hot field of database research. Query operators algorithms is a key issue for query processing performance in data stream query processing, we conduct data stream query operators algorithms in this paper.Queries on data streams consist mainly of continuous queries. In.data stream systems continuous queries have two types of execution manner: immediately execution manner and periodically execution manner. All the existing query processing algorithms on data streams are based on the immediately execution manner. But continous query based on the periodically execution manner is sometimes needed in actual practice.This paper presents query operators algorithms of sliding window. The algorithms are based on the periodically execution manner, namely in the query operators algorithms of compound sliding window, sliding window is periodically updated according to the unit of basic window. This paper mainly studys join algorithm of compound sliding, aggregate algorithm of compound sliding and join aggregate algorithm of compound sliding window.The join algorithm of compound sliding window presented in this article is a sort of symmetric join algorithm based on pipeline. We present different join algorithm by considering an effect based on the structure of basic windows. This paper proposes a simple aggregate algorithm of compound sliding window and a group aggregate algorithm of compound sliding window. The simple aggregate algorithm of compound sliding window mentioned in this paper will increase query efficiency with the method of using current aggregate answer to compute the next aggregate answer. Wepresent some algorithms by considering an effect based on the structure of basic windows for the group aggregate algorithm. This paper presents join aggregate algorithm of compound sliding window which can compute aggregate answer while computing join answer at the same time. Join aggregate algorithm of compound sliding window does not save join answer any more, thus it reduces memory cost of query operators effectively. Theory analyses and experiment results show that the algorithms proposed in this paper have very good complexity of time and space.