How to evaluate and tune the performance of PHP and MySQL indexes?

How to evaluate and tune the effect of PHP and MySQL indexes?

Introduction:
When developing and maintaining PHP and MySQL applications, optimizing database query performance is a crucial step. Indexes are one of the common means to improve query efficiency, so it is essential to evaluate and tune the effects of PHP and MySQL indexes. In this article, we will introduce how to evaluate and tune the effect of PHP and MySQL indexes, and give specific code examples.

Evaluate the effect of the index:

1. Use the EXPLAIN statement
   In MySQL, you can use the EXPLAIN statement to analyze the execution plan of the query statement. It will show how the query statement uses the index during execution. The specific usage is as follows:

   $mysqli = new mysqli('localhost', 'username', 'password', 'database');
   $query = "SELECT * FROM table_name WHERE column_name = 'value'";
   $result = $mysqli->query('EXPLAIN ' . $query);
   $row = $result->fetch_assoc();
   print_r($row);

   By viewing the output results, you can know whether the query statement uses indexes and which indexes are used.

2. Check the uniqueness of the index
   The uniqueness of the index is an important indicator for evaluating its effectiveness. If the index is not unique, its effectiveness may be greatly reduced. You can use the following code to check the uniqueness of the index:

   $mysqli = new mysqli('localhost', 'username', 'password', 'database');
   $query = "SHOW INDEX FROM table_name";
   $result = $mysqli->query($query);
   $count = 0;
   while ($row = $result->fetch_assoc()) {
    if ($row['Non_unique'] == 1) {
        $count++;
    }
   }
   echo "非唯一索引的数量：" . $count;

   By counting the number of non-unique indexes, you can initially evaluate the uniqueness of the index.

The effect of tuning indexes:

1. Add appropriate indexes
   Sometimes, query statements may fail due to lack of appropriate indexes Cause performance issues. You can add an index through the following code:

   $mysqli = new mysqli('localhost', 'username', 'password', 'database');
   $query = "ALTER TABLE table_name ADD INDEX index_name (column_name)";
   $result = $mysqli->query($query);

   Replace table_name with the actual table name, index_name with the custom index name, and column_name with the column name to which the index needs to be added.

2. Remove useless indexes
   Sometimes, there may be some outdated or useless indexes in the database, which waste storage space and affect query performance. Useless indexes can be deleted by using the following code:

   $mysqli = new mysqli('localhost', 'username', 'password', 'database');
   $query = "ALTER TABLE table_name DROP INDEX index_name";
   $result = $mysqli->query($query);

   Replace table_name with the actual table name and index_name with the index name that needs to be deleted.

Conclusion:
Evaluating and tuning the effects of PHP and MySQL indexes is an important part of optimizing database query performance. By using the EXPLAIN statement and checking the uniqueness of the index, you can initially evaluate the effect of the index. When tuning, you can improve query performance by adding appropriate indexes and removing useless indexes. Continuously evaluating and tuning indexes can make our applications more efficient and stable.

(Note: The above code examples are for reference only. Please adjust and expand according to the specific situation in actual application.)

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