A Study on Optimization of Top-k Queries in Relational Databases

Efficient execution of top-k queries is increasingly becoming a major challenge for relational database technology. Top-k query has emerged as a key requirement in modern application. In these applications, efficient and adaptive evaluation of top-k queries is an integral part of application semantics. In this paper we discuss a query optimization framework of top-k queries that fully integrates rank-join operators. Ranking queries produce results that are ordered on some computed score. A key property of top-k queries is that, users are interested only in the first k results and not in total ranking of all query results. This property directly impacts the optimization of top-k queries by optimizing for the first k results. Traditionally, most real world database systems offer the feature of first n row optimization.