Scalable Timestamp Allocation for Deadlock Prevention in Two-phase Locking based Protocols

Abstract

Concurrency control ensures the correctness of databases when transactions are processed in parallel. Bamboo is a state-of-the-art concurrency control protocol extended from 2PL Wound-Wait. One problem of Bamboo is that it requires transactions to fetch timestamps from a single centralized atomic counter. To replace the concentrated access to it, each transaction should generate timestamps independently. This paper proposes three methods of decentralization to address the problem. The first is the thread-ID method (TID), which dismisses the process of fetching timestamps entirely by assigning an ID to each thread, and transactions use the thread IDs as their timestamps. In high-contention settings, the performance of TID plummets, but the second method FairTID, which is an extension of TID, sustains the performance even in such settings. The third method (RandID) allocates timestamps using randomnumber generators. Experiments were conducted to evaluate the performance of the proposed methods. The results indicated that there were up to 62% and 59% improvement in throughput from Bamboo with FairTID and RandID, respectively. In high-contention settings, TID underperformed Bamboo, but FairTID and RandID showed consistent improvement from Bamboo.