Two research themes related to database query processing in data intensive applications are presented in this thesis. The first relates to database concurrency control in mobile computing environments and the other relates to operator scheduling in data stream systems. In the research which linked to database concurrency management mechanism, experiments are carried out to evaluate the suggested concurrency control algorithm called Read-Write Set Test for broadcast transaction.
Alternatively, two new operator scheduling algorithms for data stream systems are presented within the research. In mobile computing settings, there’s an implicit presumption that the server has the capacity to broadcast regular data to cellular consumers. Unless there’s a specific algorithm to deal with data broadcasting in a steady and well-timed manner, this assumption may not be valid. In the work, data transmission at the hosting server is formulated as a broadcast transaction that reads the entire database in a very consistent way before transmitting info to your mobile phone users in a broadcast routine. This problem isn’t trivial as the broadcast transaction creates substantial disturbance to normal update transactions on the host. Some algorithms proposed by prior reports on reading the whole databases could be candidate solutions.
However, those algorithms including Shade Test have some inadequacies in handling update transactions properly. Recently, an algorithm known as Read-Write Set Test is proposed to fix the loophole. In this research, a number of simulation tests are carried out to evaluate the performance of RWST for broadcast transaction over the wide range of system workloads. In data stream systems, the arrival structure of data streams is bursty and unstable. If a system can’t manage database query processing of tuples in an effective manner, the computer may fall into an overloaded state and might result in too many backlogged tuples waiting for database query processing. In the area of data stream systems, there are numerous investigations in the subject of query or operator scheduling.
They mainly concentrate on how to reduce memory utilization, reduce tuple delay, and increase output rate. In these investigations, the goals are focused on studying the importance of system parameters in operator scheduling and enhancing the performance and efficiency of query and operator processes by scheduling query operators to an appropriate sequence. Even there are numerous researches utilizing static factors in operator scheduling, dynamic factor might be important to operator scheduling. So in this study, dynamic elements are considered. Besides, instead of scheduling operators in an individual query as assumed in conventional approaches, new algorithms are designed to schedule all operators as a whole for all database queries in a system.
2 new scheduling algorithms are presented in this study. These are Memory Monitoring (MM) and Data Stream Grouping (DSG). MM utilizes one of the system parameters – memory usage to calculate and assign priority values to operators. MM helps to show the performance of using dynamic factors in operator scheduling. On the contrary, popular static factors (operator selectivity – s and processing time – t) are used in DSG to perform operator scheduling in multiple-query multiple-data-stream environment….
Database Query Processing
Source: City University of Hong Kong
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