• Basic use of countdownlatch and cyclicbarrier


    1 Overview CountDownLatchas well asCyclicBarrierAllJavaOne of the synchronization tools inside. This paper introduces the basic principles and basic application methods of both. 2 CountDownLatch CountDownLatchIs a synchronization tool class. Common usage scenarios include: Allows one or more threads to wait for the end of a series of other threads In the serialization task, parallelization processing […]

  • Four isolation levels of SQL92 standard


    definition Read uncommitted At the read uncommitted level, changes in transactions are visible to other transactions even if they are not committed. Transactions can read uncommitted data, which is also called dirty read. This level will cause many problems. In terms of performance, read uncommitted will not be much better than other levels, but it […]

  • When the browser sends the same request to multiple tabs


    The reason for this is that the new development younger brother wrote a blocking request in the controller and directly used while (true). When throwing an exception, the jump out condition inside will never be satisfied. (of course, we found it when we submitted the code) So we studied how he would affect the program. […]

  • What problems will the database encounter in Java?


    For database, its obvious feature is that resources can be shared by multiple users. When the same database resources are accessed by multiple users (multiple transactions) at the same time, if necessary isolation measures are not taken, it will lead to various concurrency problems and destroy the integrity of data. If isolation is not considered, […]

  • Introduction to database (8) concurrent processing


    Database concurrency control Background: database system allows multi-user operation, so there may be hundreds of transactions processed at the same time. Therefore, concurrency control must be introduced to ensure the reliability of data. In the concurrent environment, the isolation of transactions is difficult to ensure, so there will be many concurrent consistency problems. Lost modification […]

  • Summary of transaction knowledge points


    The concept of transaction: a set of database operations, either all successful or all failed; Transaction characteristics: atomicity, consistency, isolation and persistence; Possible problems when multiple transactions of the same record are executed at the same time: dirty reading, non repeatability, phantom reading; (in order to solve these problems, the concept of isolation level appears) […]

  • On transaction isolation level of MySQL | database


    Note share No matter where I am, I will reply you immediately when I see the email.My Email: echo “YUBzYW1lZ28uY29tCg==” | base64 -d preface MySQL transactions are mainly used to handle a complex business with a large amount of operations. For example, to delete a student, we should not only delete the basic information of […]

  • MySQL learning notes section 3 transaction isolation


    Transaction isolation Transaction isolation Characteristics of things: Acid Atomicity: atomicity Consistency: consistency Isolation: isolation Persistence: durability Advantages and disadvantages of isolation The higher the isolation, the lower the efficiency Isolation level of standard SQL Read uncommitted: when a transaction has not been committed, its changes can be seen by other transactions Read committed: after a […]

  • The level of MySQL transaction exception isolation


    The level of MySQL transaction exception isolation   affair While you operate the database, it is possible that other users will continue to add, delete, modify and query the data. In order to avoid the confusion of parallel, we have “transaction”. Transaction is to ensure that a group of database operations, either all successful or […]

  • MySQL transaction isolation level


    preface In short, database transaction is to ensure that a set of data operations either all succeed or all fail. In mysql, transactions are implemented in the engine layer. The native MyISAM engine does not support transactions, which is one of the important reasons why InnoDB will replace it. Isolation and isolation level When multiple […]

  • Eight pictures show what dirty writing, dirty reading, unrepeatable reading and unreal reading are all about


    We all know that MySQL supports the concurrent execution of multiple transactions. Otherwise, if one transaction is serialized one by one, the user will smash the keyboard. So, how to deal with multiple transactions writing one line of data at the same time? When a transaction is writing data, another transaction needs to read it. […]

  • Transaction isolation level in MySQL


    Transaction characteristics (acid) Atomicity(ATomicity: a transaction must be regarded as an indivisible minimum work. Hopefully, all operations in the whole transaction either commit successfully or fail to roll back. For a transaction, it is impossible to perform only part of them Consistency(CConsistency: databases always transition from one consistent state to another. Isolation(ISolution: changes made by […]