lasso lock

1. Introduction Delete Process Division search and update two stages. Lock the clustered index record in the search phase, referring to the previous article. The update phase deletes the clustered index record, then search the two-level index record, record the Garin lock on the level two index, without locking, and finally the delete label on the two-level index record. Mysql_delete:: //rr_quick->...-

It is well known that synchronized can be used to modify methods and blocks of code for classes or objects.When a code block is decorated, synchronized (object) acts on the object, constraining only that object.Synchronized (class) acts on a class, constraining all objects of the class.When modifying a method, the synchronized modifies the static method for the class. Used for objects when modifying non-static methods.Note Class and object locks are two different locks, and they do not have a sy

The following articles detail the distribution of update locks and exclusive locks during the update operation. Http://blog.csdn.net/zjcxc/article/details/27351779 According to the tracing method described in the above article, we found that in the article lock (2) -- in the process of creating and updating tables, we use sys. the results of the dm_tran_locks dynamic view are the final locking results, but the changes in the locks are not reflected.

Tags: key data Purpose value result bidirectional collation coexistence priorityA lock is a mechanism by which a computer coordinates multiple processes or a purely thread concurrently accessing a resource. in a database, data is a resource that is shared by many users in addition to the contention of traditional computing resources (CPU, RAM, I/O). How to guarantee the consistency and validity of data concurrent access is one of the problems that the

SQL Server lock type (SQL) favorites1. holdlock: Keep the shared lock on the table until the entire transaction ends, instead of releasing the added lock immediately after the statement is executed.2. nolock: no shared or exclusive locks are added. When this option takes effect, uncommitted data or "dirty data" may be read. This option is only applicable to selec

Article from http://weiba.weibo.com/10015/t/zkOgtyY0V SAP Lock MechanismI. Why should I set a lock for sap:1. Maintain Data ConsistencyIf several users want to access the same resource, they need to find a synchronous access method to maintain data consistency. For example, in the flight booking system, you need to check whether there are any empty seats. During the check, you do not want others to modify t

The locking mechanism is suitable for high concurrency scenarios: High concurrent orders, seconds kill ...Apache Stress testMySQL Lock explanationGrammarLocking: LOCK Table table name 1 read| WRITE, table name 2 read| WRITE ......... .....Unlock: UNLOCK TABLESREAD: Reading Lock | Shared Lock: All clients can only read

Classic example: Wife (Juliet) husband (Romeo), using bank cards and passbook, or internet banking, and other security issues for the same account operation. Here with multi-threaded implementation, while the simulation of the withdrawal of the implementation, using the lock interface Reentrantlock lock to ensure thread synchronization, check the withdrawal security problems, the code is as follows: -------

SQL Server lock type (SQL) Favorites 1.　　HOLDLOCK: Holds a shared lock on the table until the entire transaction ends, rather than releasing the added lock immediately after the statement is executed. 2.　　NOLOCK: No shared and exclusive locks are added, and when this option is in effect, it is possible to read UNCOMMITTED read data or "dirty data", which is on

Directory[TOC]Written in the front: May be wrong, please criticize me One, thread switching In Java, if you want to implement thread switching between threads, you need to use Thread.yield () in the thread to yield CPU time. Second, the line lock (also known as synchronous lock, mutual exclusion lock) The thread

Reprint Please specify source: http://www.cnblogs.com/skywang12345/p/3505809.htmlReadwritelock and Reentrantreadwritelock introductionReadwritelock, as the name implies, is a read-write lock. It maintains a pair of related locks--"read lock" and "write lock", one for the read operation and the other for the write operation.Read locks are used for read-only operat

SQL Server database, how to add s lock or X lock to data items I. Why should I introduce locks? When multiple users perform concurrent operations on the database, the following data inconsistency occurs: Update lossA and B read and modify the same data. The Modification result of one user destroys the Modification result of another user, such as the ticket booking system. Dirty readUser a modified the data

The cost of locking overhead locks is huge, especially for multicore multi-processing.The introduction of multi-processing, itself is to be parallelized processing to improve performance, however, because of the existence of a shared critical section, and this critical section can only have one thread access (especially for write operations), then the parallel execution flow is serialized here, visually, here seems to be a bottleneck on the Broad Road, Because serialization is inherently present

Tags: database DB21, Concept descriptionThe so-called lock upgrade (lock escalation), is a mechanism of the database, in order to save memory overhead, it will be a large number of high-resource-intensive fine-grained locks into a small amount of relatively small resources to occupy a coarse-grained lock, In most cases, the main point is to upgrade a large number

Multi-thread programming learning 4 (use of Lock), multi-thread programming lockI. Preface This article will introduce the use of Lock objects in Java 5, which can also achieve the synchronization effect, and is more convenient and flexible in use, mainly including the use of the ReentrantLock class and the use of the ReentrantReadWriteLock class.Ii. Use the ReentrantLock class 1,In java multithreading, you

Java concurrent package Lock implementation principle, java concurrent package lockIntroduction and use of Lock Lock is a thread synchronization tool introduced in java 1.5. It is mainly used to control shared resources under multiple threads. Essentially, Lock is only an interface (located in java \ util \ concurrent

In this section, we describe the lock-related APIs provided in the go language. This includes mutexes and read-write locks. We described the mutex in the 6th chapter, but did not mention the read-write lock. Both of these locks are very common and important for traditional concurrent programs. One, mutual exclusion lock Mutual exclusion

Written in front, in fact, the type and scope of database locks are affected by a variety of factors, such as database isolation level, SQL statements, whether to use primary keys, indexes, and so on. Can see the blog: http://www.cnblogs.com/zhaoyl/p/4121010.html LearnThis section describes the types of locks used by InnoDB. Shared Lock (S) and exclusive lock (X) Intent

This section is mainly about the implementation of read-write locks.As mentioned in the previous section, Readwritelock appears to have two locks: readlock/writelock. If it's really two locks, how do they affect each other?In fact, the realization of lock in Reentrantreadwritelock is done by Java.util.concurrent.locks.ReentrantReadWriteLock.Sync. This class looks familiar, in fact it is a subclass of Aqs, a similar structure that exists in Countdownla

Add by Zhj: This question did not give a satisfactory answer at the end, I have the same confusion with the questioner. Also, see mysql transaction isolation level, lockWhy is optimistic locking more efficient than pessimistic lock?Title: "The Collection" Why optimistic locking efficiency is higher than pessimistic lock? Sending station: Drink from (May 19, 2008 12:29:00 Monday), the station letter☆────────