Detailed introduction to pessimistic locking

PHP-MALL 1. Mall rush to buy, flash sale inventory oversold is a headache, the following three methods are used to prevent oversold 1. mysql lock mechanism, pessimistic lock InnoDB row-level lock scheme, not recommended, it puts more pressure on the database If a deadlock occurs, updates will never be possible unless the process is killed. 2.mysql optimistic locking This solution can be used without using a third party 3. redis incrby decrby atomic operation to prevent oversold 4. In order to facilitate expansion, the inventory class is abstracted from the interface to facilitate future expansion. You can also use other methods to implement 1.1. mysql lock mechanism, pessimistic lock, InnoDB row-level lock scheme, and query needs to use index 1. The transaction level must be SERIALIZABLE level 2. Query conditions to verify whether the inventory is sufficient for this purchase, for example: id = 1 AND inventory >=1 3. After PDO update is updated, not only must it be verified

1. Mall flash sales to prevent inventory oversold

Introduction: PHPMALL 1. Mall rush buying, flash sale inventory oversold is a headache, here are three methods to prevent oversold 1.1. mysql lock mechanism, pessimistic lock, InnoDB row level lock Solution, query needs to use index 1.2.mysql optimistic locking 1.3.redis atomic operation 2. Test 3. Problem source code address: https://github.com/jingyanlei/PHPMALL

##2 . Mysql-Detailed explanation of various lock distinctions and MVCC

Introduction: mysql locks look like There are many, and I checked most of the information, including table locks, row locks, page locks, shared locks, exclusive locks, intent locks, read locks, write locks, pessimistic locks, and optimistic locks. . I'm going, I really want to ask, are there any golden locks? I still have Fan Bingbing. . . Oops, why does it feel so messy? So let’s sort it out and summarize it. Later, there is an understanding and examples of mvcc under innodb, which is simple and easy to understand. Table/row/page-lock: table-level locking (table-level locking): M

3. MySQL database optimization (3) - MySQL pessimistic lock and optimistic lock ( Concurrency control)

Introduction: This article explains lock interpretation (shared lock), write lock (exclusive lock) ) 2. Lock granularity: table lock (table lock), row-level lock (row lock) 3. Optimistic lock and pessimistic lock pessimistic lock Exclusive lock, when a transaction operates on data, this part of the data is locked until the operation is completed After unlocking it, other transaction operations can operate on this part of the data. This will prevent other processes from reading or modifying the data in the table. Implementation: Generally use select ...for update to lock the selected data, such as

4. It is still about the issue of pessimistic locking, between begin and commit , can there be multiple fro update statements?

Introduction: Still about the issue of pessimistic locking, can there be multiple fro update statements between begin and commit?

5. A brief analysis of Oracle pessimistic locking and optimistic locking

Introduction: The pessimistic lock in Oracle is to use Oracle Connection locks the data. In Oracle, the performance loss caused by using this row-level lock is very small, just pay attention to the program

6. Optimistic locking and pessimistic locking

Introduction: Xiaojing recently submitted a PR to skynet. We discussed it for a long time before mentioning it. It is said that it was because when checking another problem, we rewritten the message scheduling part of skynet and found that in some cases, the CPU usage can be improved. Previously, Skynet's message scheduling adopted a lock-free structure based on cas. But in essence, the data structure of concurrent queue, whether it is

7. Optimistic locking and pessimistic locking

Introduction: The concept of locking has been exposed to us when we were learning multi-threading. In fact, the lock here is the same as the lock that handles concurrency in multi-threading. They both violently attribute resources to themselves. all. The purpose of using locks here is to use some mechanisms to ensure that some data will not be modified by the outside world during a certain operation. Such a mechanism, here,

8. Hibernate lock mechanism pessimistic lock, optimistic lock

Introduction: Pessimistic lock refers to a conservative attitude towards data being modified by the outside world. It is assumed that when data is accessed at any time, there may be another customer who is also accessing the same data. In order to maintain the consistency of data operations, the data is locked at the database level and relies on the lock mechanism provided by the database. . The database locking implemented based on jdbc is as follows: sele

9. SQLSERVER optimistic locking and pessimistic locking usage examples

Introduction: In an actual production environment with concurrent access by multiple users, we often need to maintain data consistency as much as possible. The most typical example is that we read data from the table, modify the data after checking and verifying, and then write it back to the database. During the reading and writing process, if in a multi-user concurrent environment, other users have already modified the data you want to modify

10. Optimistic locking and database transaction Pessimistic lock

Introduction: Optimistic locking and pessimistic locking of database things are a series of operations performed by a single logical unit of database things, which are some SQL statements, or multiple, one The update operation is a thing. Things have four characteristics: 1. Atomic things must be atomic work units, either all executed successfully (that is to say, all SQL statements are executed successfully), or none

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