Monitoring Stream Properties for Continuous Query Processing
The authors' query processor can be thought of as two separate components: a Query Execution component and a Property Monitoring component. Properties used by the Query Execution component, such as stream characteristics and plan operator behavior, are monitored by the Property Monitoring component. Of course, monitoring of operator behavior would be coupled with query execution. When significant changes are detected, the Property Monitoring component notifies the Query Execution component, which may choose to alter query plans or resource management accordingly. Note that their approach to dynamic query optimization is significantly more coarse-grained than Eddies [AH00], which makes decisions on a tuple-by-tuple level.