读锁和写锁 [英] Read Locks and Write Locks
问题描述
我不确定读写锁，只需要有人检查一下有关读写锁的事实是否正确.
I am a little unsure about read and write locks and just need someone to check if these facts about read/write locks are correct.
这通常是指数据库.
读取锁:
- 多个线程可以同时获取多个读锁.
- 当线程在行/表上具有读取锁时，没有线程可以更新/插入/删除该表中的数据.(即使试图写数据的线程不需要写锁定.)
- 行/表不能同时具有读和写锁定.
写锁:
- 当行/表具有写锁时，如果另一个线程/线程中实现了读锁，则不能被其他线程读取，但是如果没有实现读锁(例如，简单的Select查询)，则其他线程可以读取它/li>
- When a row/table has a write lock, it cannot be read by another thread if they have a read lock implemented in them but can be read by other threads if no read lock is implemented (i.e simple Select query)
感谢您的澄清.我无法在互联网上找到对这些陈述的直接断言.
Thanks for the clarification. I cant find direct assertions to these statements on the internets.
推荐答案
在数据库管理理论中，锁定用于实现多个数据库用户之间的隔离.这是缩写ACID(原子性，一致性，隔离性，耐久性)中的"I".TX(事务)将锁应用于数据，这可能会阻止其他TX在TX的生存期内访问同一数据.
In database management theory, locking is used to implement isolation among multiple database users. This is the "I" in the acronym ACID (Atomicity, Consistency, Isolation, Durability). Locks are applied by a TX (transaction) to data, which may block other TXs from accessing the same data during the TX's life.
简单锁定:可以请求两种主要类型的锁定:
Simple Locking: Two main types of locks can be requested:
- 共享锁:读取锁，即任何其他TX都可以读取但不能写入
- 排他锁:写入锁，即其他TX都无法读取或写入
- Shared lock: Read lock i.e. Any other TX can read but not write
- Exclusive lock: Write lock i.e. No other TX can read or write
多重锁定: 两相锁定(2PL)是一种可确保串行化的并发控制方法.
Multiple Locking: Two Phase Locking (2PL) is a concurrency control method that guarantees serializability.
- 增长/扩展/第一阶段:获取锁，并且不释放锁.
- 收缩/收缩/第二阶段:释放了锁定，没有获得任何锁定.
- A Growing/Expanding/First Phase: locks are acquired and no locks are released.
- A Shrinking/Contracting/Second Phase: locks are released and no locks are acquired.
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