国产av日韩一区二区三区精品,成人性爱视频在线观看,国产,欧美,日韩,一区,www.成色av久久成人,2222eeee成人天堂

Table of Contents
1. What exactly does the isolation level work?
2. Comparison of four isolation levels and applicable scenarios
3. How to set transaction isolation level?
4. Common misunderstandings and precautions
Home Database Mysql Tutorial Understanding InnoDB transaction isolation levels in MySQL

Understanding InnoDB transaction isolation levels in MySQL

Jul 02, 2025 pm 04:09 PM
innodb transaction isolation

InnoDB's transaction isolation level balances consistency and performance by controlling transaction concurrency behavior. 1. The isolation level determines the degree of visible data modification between transactions, preventing dirty reading, non-repeatable reading and phantom reading problems; 2. The four levels are Read Uncommitted (almost notable), Read Committed (performance priority), Repeatable Read (default level) and Serializable (high consistency requirements), each preventing different types of concurrency problems; 3. The isolation level at the global or session level can be set through the SET command, and it is recommended to configure it explicitly in the connection pool or ORM; 4. Notes include: the default RR is not necessarily suitable for all scenarios, the key lock under RR may cause deadlocks, and MVCC performs differently at different levels, and understanding the current level is crucial to troubleshooting problems.

Understanding InnoDB transaction isolation levels in MySQL

The transaction isolation level of InnoDB is one of the core mechanisms in MySQL that controls transaction concurrency behavior. It determines what data changes can a transaction see and how to deal with conflicting issues when multiple transactions operate the same data simultaneously.

Understanding InnoDB transaction isolation levels in MySQL

MySQL supports four standard transaction isolation levels: Read Uncommitted, Read Committed, Repeatable Read and Serializable. These levels gradually increase consistency from low to high, but also bring performance costs.

Understanding InnoDB transaction isolation levels in MySQL

1. What exactly does the isolation level work?

Simply put, the isolation level determines how well transactions see each other's modifications in a concurrent environment. for example:

  • Can you see data that has not been submitted by other transactions?
  • Will "not repeatable reading" or "illusion reading" appear?
  • Is it necessary to avoid data inconsistency through locks?

The answers to these questions depend on the isolation level you set. Choosing the right level can strike a balance between performance and consistency.

Understanding InnoDB transaction isolation levels in MySQL

2. Comparison of four isolation levels and applicable scenarios

Here is a concise comparison table that helps you quickly understand what problems each level can prevent:

Isolation level Dirty reading Cannot be read repeatedly Fantasy reading Example of usage scenario
Read Uncommitted ? ? ? Almost no use
Read Committed ? ? ? Performance priority, allow partial inconsistency
Repeatable Read ? ? ? Default level, suitable for most OLTPs
Serializable ? ? ? High data consistency requirements

illustrate:

  • Dirty Read : Read data that has not been committed by another transaction.
  • Non-Repeatable Read : The same query returns different results (because other transactions update the data).
  • Phantom Read : New records are found during range query (usually caused by insertion).

InnoDB solves the phantom reading problem through gap lock (Gap Lock) at the Repeatable Read level. This is a feature of MySQL implementation and does not necessarily comply with the SQL standard definition.


3. How to set transaction isolation level?

You can set it globally or just for the current session. Commonly used commands are as follows:

 -- Set global isolation level SET GLOBAL TRANSACTION ISOLATION LEVEL READ COMMITTED;

-- Set the isolation level of the current session SET SESSION TRANSACTION ISOLATION LEVEL REPEATABLE READ;

If you are using a connection pool or ORM framework, it is recommended to specify the isolation level explicitly in the configuration instead of relying on the default value.


4. Common misunderstandings and precautions

  • The default level is not the optimal solution
    MySQL defaults to Repeatable Read , but that doesn't mean it's suitable for all businesses. For example, some high concurrent write scenarios may prefer to use Read Committed to reduce lock competition.

  • Understand the locking mechanism under RR clearly
    The Next-Key Lock used by InnoDB under RR will lock the index records and their gaps before and after to prevent phantom reading. However, in the case of complex actual execution plans, deadlocks or blockages may be triggered.

  • MVCC and lock mechanism
    InnoDB uses multi-version concurrency control (MVCC) to optimize read operations to avoid unnecessary lock waiting. Different isolation levels can affect the visibility rules of MVCC, especially when there is a large difference between RC and RR.


Basically that's it. The isolation level does not seem complicated, but it is easy to ignore in details. Especially when tuning the production environment or troubleshooting deadlocks and data inconsistencies, it is very important to figure out which level you are currently using and why this is performed.

The above is the detailed content of Understanding InnoDB transaction isolation levels in MySQL. For more information, please follow other related articles on the PHP Chinese website!

Statement of this Website
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn

Hot AI Tools

Undress AI Tool

Undress AI Tool

Undress images for free

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Clothoff.io

Clothoff.io

AI clothes remover

Video Face Swap

Video Face Swap

Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Tools

Notepad++7.3.1

Notepad++7.3.1

Easy-to-use and free code editor

SublimeText3 Chinese version

SublimeText3 Chinese version

Chinese version, very easy to use

Zend Studio 13.0.1

Zend Studio 13.0.1

Powerful PHP integrated development environment

Dreamweaver CS6

Dreamweaver CS6

Visual web development tools

SublimeText3 Mac version

SublimeText3 Mac version

God-level code editing software (SublimeText3)

what is mysql innodb what is mysql innodb Apr 14, 2023 am 10:19 AM

InnoDB is one of the database engines of MySQL. It is now the default storage engine of MySQL and one of the standards for binary releases by MySQL AB. InnoDB adopts a dual-track authorization system, one is GPL authorization and the other is proprietary software authorization. InnoDB is the preferred engine for transactional databases and supports transaction security tables (ACID); InnoDB supports row-level locks, which can support concurrency to the greatest extent. Row-level locks are implemented by the storage engine layer.

MySQL storage engine selection comparison: InnoDB, MyISAM and Memory performance index evaluation MySQL storage engine selection comparison: InnoDB, MyISAM and Memory performance index evaluation Jul 26, 2023 am 11:25 AM

MySQL storage engine selection comparison: InnoDB, MyISAM and Memory performance index evaluation Introduction: In the MySQL database, the choice of storage engine plays a vital role in system performance and data integrity. MySQL provides a variety of storage engines, the most commonly used engines include InnoDB, MyISAM and Memory. This article will evaluate the performance indicators of these three storage engines and compare them through code examples. 1. InnoDB engine InnoDB is My

How MySQL sees InnoDB row format from binary content How MySQL sees InnoDB row format from binary content Jun 03, 2023 am 09:55 AM

InnoDB is a storage engine that stores data in tables on disk, so our data will still exist even after shutdown and restart. The actual process of processing data occurs in memory, so the data in the disk needs to be loaded into the memory. If it is processing a write or modification request, the contents in the memory also need to be refreshed to the disk. And we know that the speed of reading and writing to disk is very slow, which is several orders of magnitude different from reading and writing in memory. So when we want to get certain records from the table, does the InnoDB storage engine need to read the records from the disk one by one? The method adopted by InnoDB is to divide the data into several pages, and use pages as the basic unit of interaction between disk and memory. The size of a page in InnoDB is generally 16

How to handle mysql innodb exception How to handle mysql innodb exception Apr 17, 2023 pm 09:01 PM

1. Roll back and reinstall mysql. In order to avoid the trouble of importing this data from other places, first make a backup of the database file of the current library (/var/lib/mysql/location). Next, I uninstalled the Perconaserver 5.7 package, reinstalled the original 5.1.71 package, started the mysql service, and it prompted Unknown/unsupportedtabletype:innodb and could not start normally. 11050912:04:27InnoDB:Initializingbufferpool,size=384.0M11050912:04:27InnoDB:Complete

Explain InnoDB Full-Text Search capabilities. Explain InnoDB Full-Text Search capabilities. Apr 02, 2025 pm 06:09 PM

InnoDB's full-text search capabilities are very powerful, which can significantly improve database query efficiency and ability to process large amounts of text data. 1) InnoDB implements full-text search through inverted indexing, supporting basic and advanced search queries. 2) Use MATCH and AGAINST keywords to search, support Boolean mode and phrase search. 3) Optimization methods include using word segmentation technology, periodic rebuilding of indexes and adjusting cache size to improve performance and accuracy.

How to solve phantom reading in innoDB in Mysql How to solve phantom reading in innoDB in Mysql May 27, 2023 pm 03:34 PM

1. Mysql transaction isolation level These four isolation levels, when there are multiple transaction concurrency conflicts, some problems of dirty reading, non-repeatable reading, and phantom reading may occur, and innoDB solves them in the repeatable read isolation level mode. A problem of phantom reading, 2. What is phantom reading? Phantom reading means that in the same transaction, the results obtained when querying the same range twice before and after are inconsistent as shown in the figure. In the first transaction, we execute a range query. At this time, there is only one piece of data that meets the conditions. In the second transaction, it inserts a row of data and submits it. When the first transaction queries again, the result obtained is one more than the result of the first query. Data, note that the first and second queries of the first transaction are both in the same

How to use MyISAM and InnoDB storage engines to optimize MySQL performance How to use MyISAM and InnoDB storage engines to optimize MySQL performance May 11, 2023 pm 06:51 PM

MySQL is a widely used database management system, and different storage engines have different impacts on database performance. MyISAM and InnoDB are the two most commonly used storage engines in MySQL. They have different characteristics and improper use may affect the performance of the database. This article will introduce how to use these two storage engines to optimize MySQL performance. 1. MyISAM storage engine MyISAM is the most commonly used storage engine for MySQL. Its advantages are fast speed and small storage space. MyISA

How does InnoDB handle ACID compliance? How does InnoDB handle ACID compliance? Apr 14, 2025 am 12:03 AM

InnoDB achieves atomicity through undolog, consistency and isolation through locking mechanism and MVCC, and persistence through redolog. 1) Atomicity: Use undolog to record the original data to ensure that the transaction can be rolled back. 2) Consistency: Ensure the data consistency through row-level locking and MVCC. 3) Isolation: Supports multiple isolation levels, and REPEATABLEREAD is used by default. 4) Persistence: Use redolog to record modifications to ensure that data is saved for a long time.

See all articles