Internal and external memory set containment join

Abstract

A set containment join operates on two set-valued attributes with a subset (⊆) relationship as the join condition. It has many real-world applications, such as in publish/subscribe services and inclusion dependency discovery. Existing solutions can be broadly classified into union-oriented and intersection-oriented methods. Based on several recent studies, union-oriented methods are not competitive as they involve an expensive subset enumeration step. Intersection-oriented methods build an inverted index on one attribute and perform inverted list intersection on another attribute. Existing intersection-oriented methods intersect inverted lists one-by-one. In contrast, in this paper, we propose to intersect all the inverted lists simultaneously while skipping many irrelevant entries in the lists. To share computation, we utilize the prefix tree structure and extend our novel list intersection method to operate on the prefix tree. To further improve the efficiency, we propose to partition the data and process each partition separately. Each partition will be associated with a much smaller inverted index, and the set containment join cost can be significantly reduced. Moreover, to support large-scale datasets that are beyond the available memory space, we develop a novel adaptive data partition method that is designed to fully leverage the available memory and achieve high I/O efficiency, and thereby exhibiting outstanding performance for external memory set containment join. We evaluate our methods using both real-world and synthetic datasets. Experimental results demonstrate that our method outperforms state-of-the-art methods by up to 10× when the dataset is completely resided in memory. Furthermore, our approach achieves up to two orders of magnitude improvement on I/O efficiency compared with a baseline method when the dataset size exceeds the main memory space.