| 摘要: |
| 传统的读写事务模型（由ｒｅａｄ（ｘ）和ｗｒｉｔｅ（ｘ）序列组成）不能使调度机制充分利用应用程序的语义信息对事务进行灵活调度，从而不能有效提高系统的并发度．本文根据ＳＱＬ语言的操作语义，给出了基于ＳＱＬ的事务模型．利用这种事务模型并结合２ＰＬ方法，设计了并发控制机制：Ｃｏｎｄｉｔｉｏｎ—ｌｏｃｋｉｎｇ．这个机制可以：（１）避免数据库中的幽灵（ｐｈａｎｔｏｍ）问题，（２）利用应用程序的语义信息和完整性约束提高系统的并发度，（３）减少发生死锁的机会．因此，这是一个实用的并发控制机制． |
| 关键词: 数据库，并发控制，幽灵问题，SQL语言，两段锁 |
| DOI： |
| 分类号: |
| 基金项目:本项目受到国家863高技术项目资助. |
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| A CONCURRENCY CONTROL MECHANISM BASED ON SQL |
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Qu Yunyao,Shi Baile
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| Abstract: |
| By the standard transaction model(composed of read and write operations),the scheduler can not exploit the semantics of application programs,thus not enhancing concurrency effectively.In this paper,a new transaction model based on SQL language are presented, which can exploit the semantics of high-level operations.Depending on the the transaction model and Two-Phase Locking method,the authors design a concurrency control mechanism-Condition-Locking, which can,(1)prevent phantoms from database,(2)exploit semantic information of application programs and the knowledge of the integrity constraints of the database system to enhance. cononrrency,(3)reduce the chances of producing deadlock.Hence,it is a practical concurrency control mechanism. |
| Key words: Database,concurrency control,phantom, SQL language, two-phase locking. |
