With the prevalence of Internet access and user generated content, a large number of documents/records, such as news and web pages, have been continuously generated in an unprecedented manner. In this paper, we study the problem of efficient stream set similarity join over distributed systems, which has broad applications in data cleaning and data integration tasks, such as on-line near-duplicate detection. In contrast to prefix-based distribution strategy which is widely adopted in offline distributed processing, we propose a simple yet efficient length-based distribution framework which dispatches incoming records by their length. A load-aware length partition method is developed to find a balanced partition by effectively estimating local join cost to achieve good load balance. Our length-based scheme is surprisingly superior to its competitors since it has no replication, small communication cost, and high throughput. We further observe that the join results from the current incoming record can be utilized to guide the index construction, which in turn can facilitate the join processing of future records. Inspired by this observation, we propose a novel bundle-based join algorithm by grouping similar records on-the-fly to reduce filtering cost. A by-product of this algorithm is an efficient verification technique, which verifies a batch of records by utilizing their token differences to share verification costs, rather than verifying them individually. Extensive experiments conducted on Storm, a popular distributed stream processing system, suggest that our methods can achieve up to one order of magnitude throughput improvement over baselines.

As the prevalence of social media and GPS-enabled devices, a massive amount of geo-textual data has been generated in a stream fashion, leading to a variety of applications such as location-based recommendation and information dissemination. In this paper, we investigate a novel real-time top- k monitoring problem over sliding window of streaming data; that is, we continuously maintain the top-k most relevant geo-textual messages (e.g., geo-tagged tweets) for a large number of spatial-keyword subscriptions (e.g., registered users interested in local events ) simultaneously. To provide the most recent information under controllable memory cost, sliding window model is employed on the streaming geo-textual data. To the best of our knowledge, this is the first work to study top- k spatial-keyword publish/subscribe over sliding window. A novel system, called Skype (Top-k Spatial-keyword Publish/Subscribe), is proposed in this paper. In Skype, to continuously maintain top- k results for massive subscriptions, we devise a novel indexing structure upon subscriptions such that each incoming message can be immediately delivered on its arrival. Moreover, to reduce the expensive top- k re-evaluation cost triggered by message expiration, we develop a novel cost-based k-skyband technique to reduce the number of re-evaluations in a cost-effective way. Extensive experiments verify the great efficiency and effectiveness of our proposed techniques.

We investigate the problem of processing a large amount of continuous spatial-keyword queries over streaming data, which is essential in many applications such as location-based recommendation and advertising, thanks to the proliferation of geo-equipped devices and the ensuing location-based social media applications. For example, a location-based e-coupon system may allow potentially millions of users to register their continuous spatial-keyword queries (e.g., interests in nearby sales) by specifying a set of keywords and a spatial region; the system then delivers each incoming spatial-textual object (e.g., a geo-tagged e-coupon) to all the matched queries (i.e., users) whose spatial and textual requirements are satisfied. While there are several prior approaches aiming at providing efficient query processing techniques for the problem, their approaches belong to spatial-first indexing method which cannot well exploit the keyword distribution. In addition, their textual filtering techniques are built upon simple variants of traditional inverted indexes, which do not perform well for the textual constraint imposed by the problem. In this paper, we address the above limitations and provide a highly efficient solution based on a novel adaptive index, named AP-Tree. The AP-Tree adaptively groups registered queries using keyword and spatial partitions, guided by a cost model. The AP-Tree also naturally indexes ordered keyword combinations. We present index construction algorithm that seamlessly and effectively integrates keyword and spatial partitions. Consequently, our method adapts well to the underlying spatial and keyword distributions of the data. Our extensive experiments demonstrate that AP-Tree achieves up to an order of magnitude improvement on efficiency compared with prior state-of-the-art methods.