Effective Processing over Continuous Data Stream

Due to a late and out-of-order arrival of infinite, unbound and multiple input streams, processing continuous queries over them may lead to producing an inaccurate answer or delaying query execution. Particularly, to minimize this delay time, previous works have used timeout technique without considering the frequency of timeouts. It results in decreasing the accuracy of query execution results since the more the frequency of timeouts, the more the loss of data. We propose a AQP-SWTO method using StB that stores operator´s state and a window time-out method based on the waiting time for the next tuple by resetting the size of a queue according to the frequency of timeouts. It reduces a loss rate of data and increases the tuples output-rate. We compare AQP-SWTO method with an existing method and use output-rate and response time as criteria for performance evaluation. As a result of experiment, our proposed method shows an improvement in system performance.