Research And Implementation Of Mechanism Of Query Processing In Data Stream System

Nowadays, the theory of database is greatly developed. On the basis of traditional database, many new technologies appeared. Data stream is such an important research field which i s newly emerging. As a new and rising data model, data stream can be applied to plenty of situations because it can solve many problems in true-life. For this reason, data Stream is attractive to numerous researchers and they pay more attention to this new data model.In the model of data stream, data exists as a flowing stream rather than static data which is stored in hard disk in traditional database system. The presentation of this model is attributed to the application of sensor network and Web click stream. These special formats of data cannot be processed easily by relational database system which is mainly used to deal with static data stored in external storage. The characteristic of data stream is non-border, randomicity and unpredictability, and real time is always required in applications on data stream.Under this background, we start to research theories and applications of data stream. Our research is based on the technologies of traditional database theory and we extend these technologies to data stream by taking the peculiarity of data stream into account. We present a method of query processing over data stream, which is mainly based on the strategy of maintenance of multi-level windows. According to the strategy, we design and implement a data stream prototype system named RealStream, whose main functions are basic types of query processing over data stream. Query optimization, manifold types of windows and data sharing under the multi-stream-multi-query condition are also sustained by this system.In this thesis, we first give a survey o f current research status of theory and system of data stream. Then we show the position and functions of query processing module in data stream system. After analysising of some problemsof window structure in query processing, we present a multi-level window structure which is adopted in RealStream and shows its peculiarity, applicability and maintenance. Whereafter, we introduce the classification of window structure and give the implementation of them. The analysis and implementation of function modules of query processing in RealStream are given at the end of this thesis.