A Survey on Adaptive Query Optimization Over Data Stream
Data streams are Continuous, unbounded, rapid, time-varying streams of data elements and it Occur in a variety of modern applications such as Network monitoring and traffic engineering, Sensor networks, Telecom call records, Financial applications, Web logs and click-streams, Manufacturing processes. These stream processing applications present new challenges that are not addressed by traditional data management techniques, particularly the traditional DataBase Management System (DBMS) techniques. First, the way to measure the cost of operators in queries over data streams is different from that in the database because processing continuous queries needs new techniques and is based in memory whereas traditional processing is based on a disk. Second, continuous queries should be continually re-optimized because of the unpredictable characteristics of data streams.