Achieving both high throughput and low commit latency has long been a difficult challenge for Database Management Systems (DBMSs). As we show in this paper, existing commit processing protocols fail to fully leverage modern NVMe SSDs to deliver both high throughput and low-latency durable commits. We therefore propose autonomous commit , the first commit protocol that fully utilizes modern NVMe SSDs to achieve both objectives. Our approach exploits the high parallelism and low write latency of SSDs, enabling workers to explicitly write logs in smaller batches, thereby minimizing the impact of logging I/O on commit latency. Additionally, by parallelizing the acknowledgment procedure, where the DBMS iterates through a set of transactions to inspect their commit state, we mitigate excessive delays resulting from single-threaded commit operations in high-throughput workloads. Our experimental results show that autonomous commit achieves exceptional scalability and low-latency durable commits across a wide range of workloads.

Most Database Management Systems (DBMSs) sup-port arbitrary-sized objects through the Binary Large OBjects (BLOBs) data type. Nevertheless, application developers usually store large objects in file systems and only manage the metadata and file paths through the DBMS. This combined approach has major downsides, including a lack of transactional and indexing capabilities. Two factors contribute to the rare use of database BLOBs: the inefficiency of DBMSs in such workloads and the interoperability difficulties when interacting with external programs that expect files. To address the former, we present a new BLOB allocation and logging design that exhibits lower write amplification, reduces WAL checkpointing frequency, and consumes less storage than the conventional strategies. Our approach flushes each BLOB only once and features only a single indirection layer. Moreover, using the Filesystem in Userspace framework, BLOBs can be exposed as read-only files, allowing unmodified applications to directly access database BLOBs. The experimental results show that our design outperforms both file systems and DBMSs in handling large objects.

Increasing the concurrency level in mobile database systems has not received much attention, mainly because the concurrency requirements of mobile workloads has been regarded to be low. Contrary to popular belief, mobile workloads require higher concurrency. In this work, we propose novel journaling and concurrency mechanisms for mobile DBMSs, both of which build upon one common concept - In-Page Shadowing (IPS). We design and implement a novel In-Page Shadowing recovery method for SQLite to resolve the journaling of journal anomaly, which is known to quadruple the I/O traffic in mobile devices. IPS unions the previous and the next versions of a database page in the same physical page. Using the consolidated two versions of database page, we design Two-Version Timestamp-Ordering (2VTO) protocol that enables non-blocking reads as in multi-version concurrency control, but reduces the garbage collection overhead. Designed with mobile environments in mind, IPS and 2VTO are high-performant and resource-efficient transactional solutions. Our performance study shows that IPS and 2VTO outperform state-of-the-art logging methods and an optimistic concurrency control protocol for real mobile workloads.