Expressing and Optimizing Similarity-Based Queries in SQL

Searching for similar objects (in terms of near and nearest neighbors) of a given query object from a large set is an essential task in many applications. Recent years have seen great progress towards efficient algorithms for this task. This paper takes a query language perspective, equipping SQL with the near and nearest search capability by adding a user-definedpredicate, called NN-UDP. The predicate indicates, among a set of objects, if an object is a near or nearest-neighbor of a given query object. The use of the NN-UDP makes the queries involving similarity searches intuitive to express. Unfortunately, traditional cost-based optimization methods that deal with traditional UDPs do not work well for such SQL queries. A

• Type: Conference
• Year: 2004
• Where: ER
• Authors: Like Gao, Min Wang, Xiaoyang Sean Wang, Sriram Padmanabhan
• Keywords: ER 2004, Nearest Search Capability, Query Language Perspective, Query Object