MySQL is an open source relational database management system that is widely used in various application scenarios. When using MySQL, data log analysis is a very important technology that can help us optimize database performance, troubleshoot problems, etc. This article will introduce several commonly used data log analysis techniques to help readers better use MySQL.

1. Slow query log analysis

The slow query log is a very important type of log in MySQL. It can record SQL statements whose execution time exceeds the specified threshold. By analyzing slow query logs, we can find the source of database performance bottlenecks and optimize them.

First, you need to enable the slow query log function in the MySQL configuration file. Add the following configuration in the my.cnf file:

slow_query_log = 1
slow_query_log_file = /var/log/mysql/mysql-slow.log
long_query_time = 2

The above configuration Indicates that the slow query log function is enabled and the slow query log file is written to the /var/log/mysql/mysql-slow.log file. Statements that query for more than 2 seconds will be recorded. The query time threshold here should be adjusted according to the actual situation.

After the configuration is completed, MySQL will record each SQL statement whose execution time exceeds the threshold into the slow query log file. Next, we can use tools (such as mysqldumpslow) to analyze the logs and find bottlenecks in the query statements.

For example, the following is a slow query log sample:

Time: 2019-10-23T14:50:41.301325Z

User@Host: root[root] @ localhost []

Thread_id: 10 Schema: db QC_hits: 0

Query_time: 2.340166 Lock_time: 0.000000 Rows_sent: 1 Rows_examined: 16523

SET timestamp=1571826641;
SELECT * FROM user WHERE id > 10000;

The above log indicates that the execution time of a query was 2.34 seconds, and 16523 rows of data were scanned, but only 1 row of data was returned in the end. Database performance can be improved by optimizing the query, reducing the number of scanned rows, and optimizing query logic.

2. binlog log analysis

MySQL's binary log (binlog) is a log that records database change operations, which contains detailed information about operations such as additions, deletions, modifications, and queries. By analyzing the binlog log, we can restore historical data and reproduce the operation process.

You can view the file name and location of MySQL's current binlog log through the following command:

mysql> SHOW MASTER STATUS;

The "File" column output by the above command indicates the currently used binlog file name. Next, we can use the mysqlbinlog tool to analyze the file:

$ mysqlbinlog /var/lib/mysql/mysql-bin.000001

The above command will output all the contents in the binlog file Operation records. We can use various tools to parse these operation records, restore the database operation process or view historical data.

But it should be noted that binlog logs may have certain security risks. If binlog logs are not properly protected, sensitive database information and operation records may be exposed. Therefore, care should be taken to protect it when using this technology.

3. Error log analysis

MySQL determines errors by checking internal status and operating parameters, and records them in the error log. The error log is an important part of MySQL and can help us quickly troubleshoot and solve problems.

Common error log records include database startup and shutdown information, database user login information, error codes and error descriptions, etc. When we encounter a problem when using MySQL, we can check the error log to determine the cause of the problem and fix it.

For example, the following is a sample error log:

2019-10-23T14:50:41.301325Z 0 [ERROR] Plugin 'InnoDB' init function returned error.
2019- 10-23T14:50:41.301325Z 0 [ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed.
2019-10-23T14:50:41.301325Z 0 [ERROR] Failed to initialize plugins.
2019- 10-23T14:50:41.301325Z 0 [ERROR] Aborting

The above log indicates that the InnoDB plug-in initialization failed when MySQL was started. We can check the error log to determine the cause of the problem and try to fix it.

To sum up, MySQL is a powerful relational database management system and also has powerful data log analysis functions. By correctly using and analyzing data logs, we can optimize database performance and troubleshoot problems, thereby improving productivity and service quality.

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