Abstract
Lock managers are increasingly becoming a bottleneck in database systems that use pessimistic concurrency control. In this paper, we introduce very lightweight locking (VLL), an alternative approach to pessimistic concurrency control for main memory database systems, which avoids almost all overhead associated with traditional lock manager operations. We also propose a protocol called selective contention analysis (SCA), which enables systems implementing VLL to achieve high transactional throughput under high-contention workloads. We implement these protocols both in a traditional single-machine multi-core database server setting and in a distributed database where data are partitioned across many commodity machines in a shared-nothing cluster. Furthermore, we show how VLL and SCA can be extended to enable range locking. Our experiments show that VLL dramatically reduces locking overhead and thereby increases transactional throughput in both settings.
