Multi-version concurrency control method and system based on virtual global clock synchronization

Abstract

The invention discloses a multi-version concurrency control method and system based on virtual global clock synchronization. The method comprises the following steps: reading data; calculating and verifying a version timestamp; and writing the value written into a tuple in a set into a tuple storage position in a database, and updating the read timestamp and the write timestamp of the related tuple. The system comprises: a data reading module used for reading and copying all tuples involved in a current transaction; a timestamp calculation module used for calculating a submission timestamp ofthe current transaction according to the currently designed tuple read timestamp and write timestamp; a timestamp verification module used for verifying whether the timestamp obtained through calculation is valid or not; and a data writing module used for writing the successfully verified timestamp and the modified tuple into the database storage. The method has the following beneficial effects: the access tuples are checked, and the timestamp of each transaction is inertially calculated when the transaction is submitted, so that the limited sorting condition can be avoided.

Description

technical field [0001] The invention belongs to a database version control method, in particular to a database multi-version concurrency control method. Background technique [0002] Under the centralized lock table or timestamp manager, the locking of the table is a contention point in the database management system. By implementing these data structures in units of tuples, each transaction only locks the tuples it needs, which can significantly improve scalability. Although the memory overhead will increase, for large tuples, the overhead of these metadata (generally a few bytes) is negligible. [0003] Accessing the mutex is very expensive, requiring multiple messages on the chip. Protecting critical sections by mutexes will limit the scalability of the system, so avoid using mutexes on the critical path. The main bottleneck of the Two-PhaseLocking (2PL) algorithm lies in the centralized deadlock detector; the main bottleneck of the T / O algorithm lies in the centralize...

AI Technical Summary

Problems solved by technology

However, if transaction A is assigned a higher timestamp than transaction B, A must eventually abort because committing it would violate the principle of increasing timestamp order

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