Computing Range Consistent Answers to Aggregation Queries via Rewriting

TL;DR

This paper develops a method to compute range consistent answers to aggregation queries on databases with primary key violations by rewriting queries into first-order logic with aggregates.

Contribution

It introduces a novel rewriting approach to determine the lowest aggregated value across all repairs of inconsistent databases for certain queries.

Findings

Rewrites enable efficient computation of minimal aggregate values.

Applicable to queries with specific structures involving primary key violations.

Provides a logical framework for consistent query answering with aggregation.

Abstract

We consider the problem of answering conjunctive queries with aggregation on database instances that may violate primary key constraints. In SQL, these queries follow the SELECT-FROM-WHERE-GROUP BY format, where the WHERE-clause involves a conjunction of equalities, and the SELECT-clause can incorporate aggregate operators like MAX, MIN, SUM, AVG, or COUNT. Repairs of a database instance are defined as inclusion-maximal subsets that satisfy all primary keys. For a given query, our primary objective is to identify repairs that yield the lowest aggregated value among all possible repairs. We particularly investigate queries for which this lowest aggregated value can be determined through a rewriting in first-order logic with aggregate operators.