Toward Coordination-free and Reconfigurable Mixed Concurrency Control

Recent studies show that mixing concurrency control protocols within a single database can significantly outperform a single protocol. However, prior projects to mix concurrency control either are limited to specific pairs of protocols (e.g mixing two-phase locking (2PL) and optimistic concurrency control (OCC)) or introduce extra concurrency control overhead to guarantee their general applicability, which can be a performance bottleneck. In addition, due to unknown and shifting access patterns within a workload, candidate protocols should be chosen dynamically in response to workload changes. This requires changing candidate protocols online without having to stop the whole system, which prior work does not fully address. To resolve these two issues, we present CormCC, a general mixed concurrency control framework with no coordination overhead across candidate protocols while supporting the ability to change a protocol online with minimal overhead. Based on this framework, we build a prototype main-memory multi-core database to dynamically three popular protocols. Our experiments show CormCC has significantly higher throughput compared with single protocols and state-of-the-art mixed concurrency control approaches.