On Estimators for Aggregate Relational Algebra Queries

On Estimators for Aggregate Relational Algebra Queries

Kaizheng Du (Case Western Reserve University, USA) and Gultekin Ozsoyoglu (Case Western Reserve University, USA)
Copyright: © 1997 |Pages: 12
DOI: 10.4018/jdm.1997010103

Abstract

CASE-DB is a relational database management system that allows users to specify time constraints in queries. For an aggregate query AGG(E) where AGG is one of COUNT, SUM and AVERAGE, and E is a relational algebra expression, CASE-DB uses statistical estimators to approximate the query. This paper extends our earlier work on statistical estimators of CASE-DB with the following features: (a) new statistical estimators for COUNT queries with projection, (b) extending the methodology for SUM and AVERAGE aggregate queries, (c) new sampling plans based on systematic sampling and stratified sampling. We also present performance evaluation experiments of the estimators with the above extensions using correlated and uncorrelated database instances.

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