Explain the purpose and usage of the MySQL Performance Schema.

MySQL Performance Schema is a tool for monitoring and optimizing database performance. Its functions include identifying performance bottlenecks and optimizing queries. 1) Enable Performance Schema by updating the setup_instruments table. 2) The basic usage includes viewing the current query and waiting for events. 3) Advanced usage involves analyzing the most frequent queries to optimize performance.

introduction

When we talk about performance optimization of databases, MySQL Performance Schema is definitely a tool that cannot be ignored. It is like a database health monitor, which can have an in-depth understanding of the operating status of MySQL. Today, I will take you into the deepest discussion of the purpose and usage of MySQL Performance Schema. I hope that through this article, you can master how to use it to improve the performance of your database.

Review of basic knowledge

MySQL Performance Schema is a monitoring tool that comes with MySQL database, which is mainly used to collect performance data inside the database. It appears to help database administrators and developers better understand and optimize the database's operating efficiency. Before understanding Performance Schema, we need to understand some basic concepts, such as MySQL threads, events, tables, etc. These are the objects monitored by Performance Schema.

Core concept or function analysis

The definition and function of MySQL Performance Schema

MySQL Performance Schema can be regarded as the "black box" of the MySQL database, which records various activities within the database, including but not limited to queries, locks, file I/O, etc. Its main function is to help us identify performance bottlenecks, optimize query and overall database performance.

To give a simple example, if you find that some queries run particularly slowly when using MySQL, through Performance Schema, you can view the specific execution of these queries and find out the problem.

 -- Enable Performance Schema
UPDATE performance_schema.setup_instruments SET ENABLED = 'YES', TIMED = 'YES' WHERE NAME LIKE 'stage/%';

How it works

Performance Schema works by monitoring activities inside MySQL through a series of "probes". These probes record the start and end times of the event, thus calculating the duration of the event. Performance Schema can also record details such as waiting time of events, CPU usage, and more.

In implementation, Performance Schema uses a series of tables to store this data, which can be accessed through SQL queries. For example, events_waits_current table records the currently waiting events, while the events_statements_summary_by_digest table provides performance data summarized by statement summary.

Example of usage

Basic usage

The most common usage is to see the currently executing queries and their waiting conditions. Here is a simple example:

 -- View the currently executing query SELECT * FROM performance_schema.events_statements_current;

-- View the currently waiting event SELECT * FROM performance_schema.events_waits_current;

These queries can help you quickly understand the current running status of the database and identify possible performance bottlenecks.

Advanced Usage

For experienced users, Performance Schema can be used to perform more in-depth performance analysis. For example, you can use the events_statements_summary_by_digest table to analyze which queries are executed most frequently in the database and find out the average execution time of these queries.

 -- Analysis of the most frequent queries SELECT DIGEST_TEXT, COUNT_STAR, SUM_TIMER_WAIT / COUNT_STAR AS AVG_TIME
FROM performance_schema.events_statements_summary_by_digest
ORDER BY COUNT_STAR DESC LIMIT 10;

This query can help you find out frequently executed but potentially inefficient queries for optimization.

Common Errors and Debugging Tips

Common problems when using Performance Schema include performance degradation after enabled or failure to obtain expected data. Here are some debugging tips:

• Performance Degradation : If the database performance degradation after enabling Performance Schema, it may be due to excessive monitoring scope. You can adjust the settings in setup_instruments and setup_consumers tables, and enable only the necessary monitoring items.
• Data acquisition problem : If the expected data cannot be obtained, it may be because some events are not enabled. You can check and enable the corresponding events through setup_instruments table.

Performance optimization and best practices

In practical applications, how to use Performance Schema for performance optimization is a key issue. Here are some suggestions:

• Compare performance differences between different methods : For example, you can use Performance Schema to compare the effects of different indexing strategies. Through the events_statements_summary_by_digest table, you can see the execution time of different queries, thereby selecting the optimal indexing strategy.

 -- Comparison of the effects of different index strategies SELECT DIGEST_TEXT, INDEX_USED, SUM_TIMER_WAIT / COUNT_STAR AS AVG_TIME
FROM performance_schema.events_statements_summary_by_digest
WHERE DIGEST_TEXT LIKE '%SELECT%';

• Programming Habits and Best Practices : When using Performance Schema, it is important to keep the code readable and maintained. Try to use clear query statements and add comments if necessary so that other developers or database administrators can understand your intentions.

Overall, MySQL Performance Schema is a powerful tool that helps us gain insight into the performance of our database. Through reasonable use and optimization, we can significantly improve the database operation efficiency. Hopefully this article provides you with some useful insights and practical experience.

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