Admissible Record-Oriented Evaluation Plans for Declarative Updates

Efflcient evaluation strategies for declarative updates have rarely been investigated. Due to possible dependencies between the resulting database state and the order in which records (objects) are processed, usually declarative updates are evaluated in a set-oriented way in order to ensure a deterministic evaluation. In this paper, we show that such dependencies can be detected by exploiting knowledge about conflicts between the operations that are used to access the database during the update evaluation. Thus most declarative updates can also be evaluated deterministically, and in some cases more efflciently, in a record-oriented way. We show that some of the detected conflicts can be relaxed or even be ignored, while a deterministic evaluation can still be guaranteed.