【摘要】 连接拥塞、负载不均衡和临时性网络中断,使得传统查询处理技术难以处理广域网下的数据连接。无阻塞连接查询算法通过调用后台进程能够有效处理不稳定网络中的不确定性并隐藏数据到达的中断情况。因为逐渐增长的外存数据难以在较短的时间间隔内被一次性处理完,所以像XJoin这样的经典无阻塞连接算法不能很好地处理间隔时间较短的不稳定网络下的查询连接。提出一种新的无阻塞连接算法XJoin-FG,将一次粗粒度的事务根据间隔时间分解为多个部分,并且采用细粒度的时间戳来避免重复数据结果的产生。仿真实验采用Internet上的跟踪数据,结果表明XJoin-FG即使在处理很长的数据块时也能够迅速地反馈查询结果。更多还原

【Abstract】 Wide-area distribution raises significant performance problems for traditional query processing techniques as data access becomes less predictable due to link congestion,load imbalances,and temporary outages.Non-blocking joi-ning query execution is a promising approach to coping with unpredictability in unreliable network and hiding intermi-ttent delays in data arrival by reactively scheduling background processing.Classical non-blocking two-way joining technique such as XJoin fail to deliver acceptable performance in such a scenario where gradually augmenting partition could not be dealt with during one relatively short intermittent delay.We developed a novel reactively-scheduled non-blocking join,called XJoin-FG,disparting one coarse-grained transaction into several parts according to the size of interval time.XJoin-FG employed fine-grained timestamp mechanism to avoid duplicate results.Using the optimization implementation along with emulational data obtained by monitoring Internet data delivery,we show that XJoin-FG is an effective solution for providing fast query responses to users even in the presence of the longer-term of data sources appeared as una-vailability.更多还原