Share a method to solve the MySQL deadlock problem
1. Environment
CentOS, MySQL 5.6.21-70, JPA
Problem scenario: The system has a scheduled batch update data status operation, updating thousands of records each time, and the total number of records in the table is about 5 million.
2. Error log
2017-2-25 17:38:41 org.hibernate.util.JDBCExceptionReporter logExceptions 严重: Lock wait timeout exceeded; try restarting transaction 2017-2-25 17:39:05 org.hibernate.util.JDBCExceptionReporter logExceptions 警告: SQL Error: 1213, SQLState: 40001 2017-2-25 17:39:05 org.hibernate.util.JDBCExceptionReporter logExceptions 严重: Deadlock found when trying to get lock; try restarting transaction
3. Troubleshooting
Check InnoDB status for locks mysql> SHOW ENGINE InnoDB STATUS; Check MySQL open tables mysql> SHOW OPEN TABLES WHERE In_use > 0; Check pending InnoDB transactions mysql> SELECT * FROM `information_schema`.`innodb_trx` ORDER BY `trx_started`; Check lock dependency - what blocks what mysql> SELECT * FROM `information_schema`.`innodb_locks`;
After troubleshooting, it was found that problems occurred when executing statements similar to this:
update t_task_tel set state='iok', update_date='2017-02-27 11:03:02' where tel_id=66042 and task_id=350199;
4. Analysis
After searching for relevant information, I found that MySQL InnoDB does not necessarily all have row-level locks.
Relevant reference material fragments are as follows:
Lock selection
1), if the update condition does not go through the index, for example, execute "update from t1 set v2=0 where v2=5;", At this time, a full table scan will be performed. When scanning the table, any other update operations must be prevented, so it is upgraded to a table lock.
2) If the update condition is an index field, but it is not a unique index (including the primary key index), for example, if you execute "update from t1 set v2=0 where v1=9;"
then the update will Use Next-Key Lock. Reasons for using Next-Key Lock:
a), first ensure that an exclusive lock is added to the records that meet the conditions, which will lock the value of the current non-unique index and the corresponding primary key index;
b), and also It is guaranteed that new data cannot be inserted into the locked interval.
3) If the update condition is a unique index, use Record Lock.
InnoDB finds the corresponding record based on the unique index, and adds the record lock to the primary key index value and the unique index value. But do not use Gap Lock (gap lock).
Since InnoDB defaults to Row-Level Lock, MySQL will execute Row lock (only lock the selected data) only if the primary key is "clearly" specified. Otherwise, MySQL will execute Table Lock (lock the entire data). The form is locked).
According to the analysis conclusion, it is guessed that the reason is that tel_id and task_id did not establish UNIQUE (unique index) in the Where condition when updating the _task_tel table;
5. Solution
Based on this analysis, try to solve the problem by establishing UNIQUE (unique index) through the two fields of tel_id and task_id. (You can also query it first and then update it based on the primary key ID, so that the large amount of data in the table will not affect online business).
After solving this problem, the problem has not recurred.
If your problem is similar to what I encountered, you can try to solve it accordingly.

This article explores optimizing MySQL memory usage in Docker. It discusses monitoring techniques (Docker stats, Performance Schema, external tools) and configuration strategies. These include Docker memory limits, swapping, and cgroups, alongside

This article addresses MySQL's "unable to open shared library" error. The issue stems from MySQL's inability to locate necessary shared libraries (.so/.dll files). Solutions involve verifying library installation via the system's package m

The article discusses using MySQL's ALTER TABLE statement to modify tables, including adding/dropping columns, renaming tables/columns, and changing column data types.

This article compares installing MySQL on Linux directly versus using Podman containers, with/without phpMyAdmin. It details installation steps for each method, emphasizing Podman's advantages in isolation, portability, and reproducibility, but also

This article provides a comprehensive overview of SQLite, a self-contained, serverless relational database. It details SQLite's advantages (simplicity, portability, ease of use) and disadvantages (concurrency limitations, scalability challenges). C

Article discusses configuring SSL/TLS encryption for MySQL, including certificate generation and verification. Main issue is using self-signed certificates' security implications.[Character count: 159]

This guide demonstrates installing and managing multiple MySQL versions on macOS using Homebrew. It emphasizes using Homebrew to isolate installations, preventing conflicts. The article details installation, starting/stopping services, and best pra

Article discusses popular MySQL GUI tools like MySQL Workbench and phpMyAdmin, comparing their features and suitability for beginners and advanced users.[159 characters]


Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

AI Hentai Generator
Generate AI Hentai for free.

Hot Article

Hot Tools

mPDF
mPDF is a PHP library that can generate PDF files from UTF-8 encoded HTML. The original author, Ian Back, wrote mPDF to output PDF files "on the fly" from his website and handle different languages. It is slower than original scripts like HTML2FPDF and produces larger files when using Unicode fonts, but supports CSS styles etc. and has a lot of enhancements. Supports almost all languages, including RTL (Arabic and Hebrew) and CJK (Chinese, Japanese and Korean). Supports nested block-level elements (such as P, DIV),

SublimeText3 Linux new version
SublimeText3 Linux latest version

Notepad++7.3.1
Easy-to-use and free code editor

PhpStorm Mac version
The latest (2018.2.1) professional PHP integrated development tool

Dreamweaver CS6
Visual web development tools
