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MySQL is a commonly used open source relational database management system that is widely popular among users due to its ease of use and reliability. But in high concurrency situations, MySQL will also have some problems, such as .lock waiting and deadlock. This article will introduce how to discover and solve concurrency problems in MySQL database.
1. The occurrence of concurrency problems
When multiple users access the MySQL database at the same time and try to modify data, concurrency problems will occur. For example, user A is modifying a certain row of data in the database, and user B also wants to modify the same row of data. The requests of these two users arrive at the database at the same time, but only one user can successfully modify the data, because in MySQL only one user can execute the UPDATE statement at the same time. If MySQL does not handle this situation, it will cause two users to update the same data at the same time, causing data inconsistency problems.
2. How to detect concurrency problems
In MySQL, you can use a variety of methods to detect concurrency problems. Here are some commonly used methods.
You can use the following command to view all currently running queries:
SHOW PROCESSLIST;
This command will display the current MySQL server All active processes, including running queries, blocking requests, etc. You can use the following command to check which queries run for too long:
SELECT ID, USER, HOST, DB, COMMAND, TIME, STATE, INFO FROM information_schema.processlist WHERE TIME > 10 ORDER BY TIME DESC;
This command will list all queries that run for more than 10 seconds, and use the status in the STATE column to determine whether concurrency problems have occurred.
Deadlock is a common problem in MySQL concurrency issues. You can use the following command to check if there is a deadlock:
SHOW ENGINE INNODB STATUSG
This command will return the details of the InnoDB storage engine, including the current deadlock situation. You can locate the deadlock problem by looking for the "LATEST DETECTED DEADLOCK" mark. .
When concurrency problems occur, it may be that server resources are exhausted, resulting in performance degradation. Therefore, monitoring of system resources can detect concurrency issues faster. You can monitor system resource usage using the following command:
top
This command by default will list details of currently running processes along with resource usage.
3. How to solve concurrency problems
When concurrency problems occur, they need to be solved according to the specific situation. Several common methods are introduced below:
By optimizing the query, you can reduce the execution time of the query, thereby reducing the burden on the MySQL server. Methods to optimize queries include adding indexes, using smaller queries to return less data, reducing Join operations, etc.
Distribute data to multiple servers, and each server is responsible for a part of the data. This can limit the number of concurrencies on a single server, thereby reducing Possibility of concurrency conflicts.
For large-scale concurrent requests, it may be necessary to improve the hardware configuration of the MySQL server, such as increasing memory, strengthening the CPU, etc.
In short, when a concurrency problem occurs, we should first find the source of the problem, and then use reasonable solutions to gradually solve the problem. In daily operations, optimization should also be carried out frequently to avoid concurrency problems.
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