Vector search is widely employed in recommendation systems, search engines, etc. With the explosive growth of online data and streaming processing engines, streaming vector search has attracted increasing research attention. However, prevailing vector search systems like Vearch, Vespa, and Milvus typically operate as external batch services for streaming processing requirements, resulting in sub-optimal performance for streaming processing scenarios. In this paper, we propose VStream, a distributed streaming vector search system. Implementing such a system is non-trivial, raising three technical challenges in streaming adaptability, system scalability, and real-time response. Specifically, VStream offers a dynamic partitioner that adapts to data distribution changes in vector streams. Additionally, VStream features an effective hierarchical storage architecture facilitated by streaming state management, enabling a hybrid of four-level storage media with diverse access speeds and targets. Furthermore, VStream utilizes dynamic hot-cold patterns, such as access frequency, in the streaming vector data, incorporating a specialized hot-cold separation mechanism to enhance query efficiency. Extensive experiments prove that VStream outperforms existing vector search systems, e.g., achieving 251–373× improvements in query efficiency, 2.2–2.5× savings in CPU usage, and 1.5–2.0× reductions in memory overhead.

Materialized views (MVs) are critical for improving query performance of database systems, especially in online analytical processing (OLAP) databases. Typically, MVs are maintained by DBAs, which relies on prior knowledge and manual operations. Recently, autonomous solutions are designed for specific databases. However, a data warehouse for OLAP is typically hierarchical, which uses different database engines at different stages. Hence, existing methods have limitations in terms of autonomy and unification to support practical applications. Motivated by these, we develop UniView, a unified autonomous materialized view management system that supports various popular databases, including Spark SQL, PostgreSQL, and ClickHouse. Moreover, we provide a cross-platform web user interface, where users can carry out the process of materialized views and evaluate the optimization performance. In the demonstration, we show that UniView is user-friendly and can achieve superior performance in the practical industry scenarios.

With the explosive ubiquity of GPS-equipped devices, e.g., mobile phones, vehicles, and vessels, a massive amount of real-time, unbounded, and varying-sampling trajectory streams are being generated continuously. Clustering trajectory streams is useful in real-life applications, such as traffic congestion prediction, crowd flow detection, and moving behavior study. Although several sliding-window based algorithms (that adopt the classic two-phases online-offline processing framework) are proposed for trajectory stream clustering, three challenges exist to meet ever-increasing application demands for effective, efficient, and scalable online clustering: i) How to effectively model unbounded trajectory streams in the online settings for effective clustering? ii) How to achieve truly real-time online processing? iii) How to improve the scalable capability of the clustering algorithm to support large-scale moving trajectory streams? In this paper, we propose an efficient and distributed trajectory stream clustering framework that can: i) model trajectory streams dynamically and effectively in a self-adaptive manner, i.e.,$k$-Segment, which considers both spatial and temporal aspects of trajectory streams, ii) support distributed indexing, processing, and workload balance, and iii) incrementally cluster trajectory streams in an efficient manner. Experiments on a wide range of real-world trajectory datasets show that our framework outperforms state-of-the-art baselines in terms of clustering quality, efficiency, and scalability.

Trajectory similarity queries, including similarity search and similarity join, offer a foundation for many geo-spatial applications. With the rapid increase of streaming trajectory data volumes, e.g., data from mobile phones, vessel monitoring, or traffic systems, many location-based services benefit from online similarity analytics over trajectory data streams, where moving objects continually emit real-time position data. However, most existing studies focus on offline settings, and thus several major challenges remain unanswered in an online setting. To this end, we describe Ghost, a distributed stream processing framework that enables generic, efficient, and scalable online trajectory similarity search and join. We propose a novel incremental online similarity computation (IOSC) mechanism to accelerate pair-wise streaming trajectory distance calculation, which supports a broad range of trajectory distance metrics. Compared with previous studies, IOSC reduces the complexity from quadratic to linear in terms of trajectory length. Building on this foundation, we propose histogram-based algorithms that exploit histogram indexes and a series of pruning bounds to enable streaming trajectory similarity search and join. Finally, we extend our methods to the distributed platform Flink for scalability, where a CostPartitioner is developed to ensure parallel processing and workload balancing. An experimental study using two real-life and one synthetic datasets shows that Ghost (i) acquires 6-20× efficiency/throughput gains and one order of magnitude memory overhead savings over state-of-the-art baselines, (ii) achieves 3--8× workload balancing gains on Flink, and (iii) exhibits low parameter sensitivity and high robustness.