Rebirth-Retire: A Concurrency Control Protocol Adaptable to Different Levels of Contention

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Abstract

The Wound-Retire concurrency control protocol was proposed to reduce contention for hotspots in in-memory databases. It enhances throughput under high-contention scenarios by allowing transactions to release their locks earlier (referred to as Retire ), thereby reducing the wait times for other transactions. However, the proactive early release of locks introduces additional overhead, making it less efficient than other lock-based protocols in low-contention scenarios. Moreover, the wound strategy it adopts, while effective at preventing deadlocks, may lead to unnecessary transaction aborts. To address these issues, this paper proposes the Rebirth-Retire concurrency control protocol as an enhancement to the WoundRetire protocol. In this protocol, a lock is retired by a younger transaction that requests it, which reduces unnecessary retire costs in low-contention scenarios. Additionally, rather than aborting younger transactions, older transactions are assigned larger timestamps (referred to as Rebirth ), unless doing so would result in a deadlock. Experimental evaluations demonstrate that the RebirthRetire protocol achieves better throughput and lower abort rate than the Wound-Retire protocol across varying levels of contention workloads.