【摘要】 在需要处理数据流的应用系统中,数据流的达是持续的、无界的,传统对静态数据库进行分块查询处理的方式已不再适应这种数据流的无穷性.本文针对数据流持续查询应用的不同场合,提出在查询中使用滑动窗口、带符号的数据流及断言窗口机制,使传统的查询处理加上这些机制后能适应数据流的查询处理.更多还原

【Abstract】 For the applications that require real-time processing of high-volume data streams,two classes of query operators in traditional database management system are impractical for processing long or infinite data streams.Unbounded stateful operators maintain state with no upper bound in size and,so,run out of memory.Blocking operators read an entire input before emitting a single output and,so,might never produce a result.We discuss the semantics of sliding-windows,punctuated streams and predicate-window.Sliding-windows define a window at any point of time contains a historical snapshot of a finite portion of the stream.A punctuation is a predicate that describes a subset of tuples.The predicate-window includes the input stream tuples that satisfy a given predicate.更多还原