Presto is an open source distributed query engine used widely at Facebook, Uber, Twitter, Pinterest, and many other internet companies. Since open sourced in 2013, the Presto community has made several rounds of design and implementations, to support a variety of use cases, including interactive analytics, real time reporting and dashboard, ETL workloads, A/B testing, monitoring and alerts, etc. In this paper, we'd like to introduce some of the most important features and performance improvements the open source Presto community made in recent years, which enables companies running Presto at scale, supporting millions of queries per day, with hundreds of thousands of machines. Specifically, how Presto provides unified SQL on heterogeneous storage systems without data copy; how Presto deals with complex data, including nested columnar data and schema evolution; How Presto supports geospatial queries efficiently, and how file list cache works in Presto. We also talk about cluster federation, and Presto on cloud. Experimental results and our production experience could help others running interactive SQL systems at scale.

Although memory is an important constraint in embedded sensor nodes, existing embedded applications and systems are typically designed to work under the memory constraints of a single platform and do not consider the interplay between memory and flash storage. In this paper, we present the design of a memory-adaptive flash-based embedded sensor system that allows an application to exploit the presence of flash and adapt to different amounts of RAM on the embedded device. We describe how such a system can be exploited by data-centric sensor applications. Our design involves several novel features: flash and memory-efficient storage and indexing, techniques for efficient storage reclamation, and intelligent buffer management to maximize write coalescing. Our results show that our system is highly energy-efficient under different workloads, and can be configured for embedded sensor platforms with memory constraints ranging from a few kilobytes to hundreds of kilobytes.

Flash memories are in ubiquitous use for storage on sensor nodes, mobile devices, and enterprise servers. However, they present significant challenges in designing tree indexes due to their fundamentally different read and write characteristics in comparison to magnetic disks. In this paper, we present the Lazy-Adaptive Tree (LA-Tree), a novel index structure that is designed to improve performance by minimizing accesses to flash. The LA-tree has three key features: 1) it amortizes the cost of node reads and writes by performing update operations in a lazy manner using cascaded buffers, 2) it dynamically adapts buffer sizes to workload using an online algorithm, which we prove to be optimal under the cost model for raw NAND flashes, and 3) it optimizes index parameters, memory management, and storage reclamation to address flash constraints. Our performance results on raw NAND flashes show that the LA-Tree achieves 2x to 12x gains over the best of alternate schemes across a range of workloads and memory constraints. Initial results on SSDs are also promising, with 3x to 6x gains in most cases.

In this paper, we address the problem of video multicasting in ad hoc wireless networks. The salient characteristics of video traffic make conventional multicasting protocols perform quite poorly, hence warranting application-centric approaches in order to increase robustness to packet losses and lower the overhead. By exploiting the path-diversity and the error resilience properties of multiple description coding (MDC), we propose a robust demand-driven video multicast routing (RDVMR) protocol. Our protocol uses a novel path based Steiner tree heuristic to reduce the number of forwarders in each tree, and constructs multiple trees in parallel with reduced number of common nodes among them. Moreover, unlike other on-demand multicast protocols, RDVMR specifically attempts to reduce the periodic (non on-demand) control traffic. We extensively evaluate RDVMR in the NS2 simulation framework and show that it outperforms existing single-tree and two-tree multicasting protocols.