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Admissible Record-Oriented Evaluation Plans for Declarative Updates
 

Summary: Admissible Record-Oriented Evaluation Plans
for Declarative Updates
Gisela Fischer
Dresdner Bank AG, 60301 Frankfurt a.M., Germany
E-Mail: Gisela.Fischer@dresdner-bank.com
Karl Aberer
GMD-IPSI, Dolivostrasse 15, 64293 Darmstadt, Germany
E-Mail: aberer@darmstadt.gmd.de
Abstract
Efficient 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 efficiently, 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.
1 Introduction
Different approaches for optimizing and evaluating declarative queries have been proposed so far (comprehensive
overviews can be found in [10] and [6]). Many query languages like SQL[9], QUEL[15] or POSTQUEL[13] also pro-
vide means for a declarative specification of database updates. However, particular strategies for the optimization and

  

Source: Aberer, Karl - Faculté Informatique et Communications, Ecole Polytechnique Fédérale de Lausanne

 

Collections: Computer Technologies and Information Sciences