Preface

7th International Conference on Similarity Search and Applications (SISAP).\ud Los Cabos, México. 29-31 october 2014

Efficient processing of similarity queries with applications

Today, a myriad of data sources, from the Internet to business operations to scientific instruments, produce large and different types of data. Many application scenarios, e.g., marketing analysis, sensor networks, and medical and biological applications, call for identifying and processing similarities in big data. As a result, it is imperative to develop new similarity query processing approaches and systems that scale from low dimensional data to high dimensional data, from single machine to clusters of hundreds of machines, and from disk-based to memory-based processing. This dissertation introduces and studies several similarity-aware query operators, analyzes and optimizes their performance. The first contribution of this dissertation is an SQL-based Similarity Group-by operator (SGB, for short) that extends the semantics of the standard SQL Group-by operator to group data with similar but not necessarily equal values. We realize these SGB operators by extending the Standard SQL Group-by and introduce two new SGB operators for multi-dimensional data. We implement and test the new SGB operators and their algorithms inside an open-source centralized database server (PostgreSQL). In the second contribution of this dissertation, we study how to efficiently process Hamming-distance-based similarity queries (Hamming-distance select and Hamming-distance join) that are crucial to many applications. We introduce a new index, termed the HA-Index, that speeds up distance comparisons and eliminates redundancies when performing the two flavors of Hamming distance range queries (namely, the selects and joins). In the third and last contribution of this dissertation, we develop a system for similarity query processing and optimization in an in-memory and distributed setup for big spatial data. We propose a query scheduler and a distributed query optimizer that use a new cost model to optimize the cost of similarity query processing in this in-memory distributed setup. The scheduler and query optimizer generates query execution plans that minimize the effect of query skew. The query scheduler employs new spatial indexing techniques based on bloom filters to forward queries to the appropriate local sites. The proposed query processing and optimization techniques are prototyped inside Spark, a distributed main-memory computation system

The similarity-aware relational intersect database operator

Identifying similarities in large datasets is an essential operation in many applications such as bioinformatics, pattern recognition, and data integration. To make the underlying database system similarity-aware, the core relational operators have to be extended. Several similarity-aware relational operators have been proposed that introduce similarity processing at the database engine level, e.g., similarity joins and similarity group-by. This paper extends the semantics of the set intersection operator to operate over similar values. The paper describes the semantics of the similarity-based set intersection operator, and develops an efficient query processing algorithm for evaluating it. The proposed operator is implemented inside an open-source database system, namely PostgreSQL. Several queries from the TPC-H benchmark are extended to include similarity-based set intersetion predicates. Performance results demonstrate up to three orders of magnitude speedup in performance over equivalent queries that only employ regular operators.NPRP grant 4-1534-1-247 from the Qatar National Research Fund and by the National Science Foundation Grants IIS 0916614, IIS 1117766, and IIS 0964639.Scopu