How to monitor query performance of MySQL database?

How to monitor query performance of MySQL database?

In order to optimize the query performance of the MySQL database, we need to understand the execution efficiency of the query and the resources it consumes. In practical applications, a variety of methods can be used to monitor and analyze the query performance of the MySQL database to identify performance bottlenecks and optimize them.

1. Use the Explain statement to analyze the query plan

The Explain statement can display the query plan of the MySQL database to execute the query statement, that is, how the database executes the query. By analyzing the output of Explain, we can understand the query execution method, index usage, table access sequence and other information. The following is an example of using the Explain statement to analyze the query plan:

EXPLAIN SELECT * FROM users WHERE age > 25;

The output of Explain includes the following important fields:

• id: The sequence number of the query, each query statement All have a unique id.
• select_type: Query type, including SIMPLE (simple query), PRIMARY (main query), SUBQUERY (subquery), etc.
• table: The name of the table involved in the query.
• type: Access type, such as ALL (full table scan), INDEX (index scan), RANGE (range scan), REF (index reference), etc.
• possible_keys: Possible indexes to use.
• key: The actual index used.
• rows: The number of rows scanned.
• Extra: Extra information, such as Using index (using index), Using where (using WHERE condition), etc.

By analyzing the output of Explain, we can judge the execution efficiency of the query statement and the usage of related indexes, so as to optimize performance.

2. Use the slow query log

MySQL provides the slow query log function, which can record query statements whose execution time exceeds the specified threshold. By turning on the slow query log function, we can locate query statements that take a long time to execute and perform performance optimization. The following is an example of enabling the slow query log:

SET global slow_query_log = ON;
SET global long_query_time = 1;

In the above example, the slow query log is enabled, and query statements that take more than 1 second to execute are set as slow queries.

The output of the slow query log includes the execution time of the query statement, index usage, access method and other information. By analyzing slow query logs, we can find query statements that take longer to execute and optimize them as needed.

3. Use performance analysis tools

MySQL provides multiple performance analysis tools that can help us monitor and analyze the query performance of the database. For example, you can use the Performance Schema that comes with MySQL to collect query execution time, locks and other information. The following is an example of using Performance Schema:

SET global performance_schema = ON;
SELECT * FROM performance_schema.events_stages_summary_by_thread_by_event_name WHERE thread_id = CONNECTION_ID();

In the above example, Performance Schema is turned on and the query performance information of the current thread is queried.

In addition to Performance Schema, there are other performance analysis tools, such as pt-query-digest, EXPLAIN ANALYZE, etc., which can help us analyze the query performance of the MySQL database more deeply.

Conclusion

By using the above methods, we can effectively monitor and analyze the query performance of the MySQL database and identify potential performance bottlenecks for optimization. The article only briefly introduces some of these methods, and the actual situation may be more complex. In practical applications, we need to choose appropriate methods to monitor and analyze query performance and perform performance optimization based on specific business needs and database configuration.

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