这篇文章主要为大家展示了“Percona 5.5如何定位未使用的索引",内容简而易懂，条理清晰，希望能够帮助大家解决疑惑，下面让小编带领大家一起研究并学习一下“Percona 5.5如何定位未使用的索引"这篇文章吧。
打开userstat参数，然后让关系型数据库运行一段时间。
之后可以在信息模式。索引_统计表中查询到索引的使用频率。
关系型数据库显示像%用户%这样的全局变量；
- -
|变量名|值|
- -
| userstat | OFF |
- -
一行一组(0.00秒)
关系型数据库从信息模式。索引_统计中选择*;
空集(0.00秒)
关系型数据库设置全局用户stat=1；
查询正常，0行受影响(0.00秒)
关系型数据库显示像%用户%这样的全局变量；
- -
|变量名|值|
- -
| userstat | ON |
- -
一行一组(0.00秒)
关系型数据库从信息模式。索引_统计中选择*;
空集(0.00秒)
关系型数据库解释从电磁脉冲中选择*其中雇佣日期' 1982-01-01 '和deptno=20
- - - - - - - - - -
| id | select _ type | table | type | optional _ keys | key | key _ len | ref | row | Extra |
- - - - - - - - - -
| 1 | SIMPLE | EMP | range | idx _ date _ sal _ job，idx _ date | idx _ date _ sal _ job | 4 | NULL | 3 |使用哪里|
- - - - - - - - - -
一行一组(0.00秒)
mysql> select * from information_schema.index_statistics;
Empty set (0.00 sec)
mysql> select * from emp where hiredate > '1982-01-01' and deptno = 20;
+-------+-------+---------+------+---------------------+------+------+--------+
| empno | ename | job | mgr | hiredate | sal | comm | deptno |
+-------+-------+---------+------+---------------------+------+------+--------+
| 7788 | SCOTT | ANALYST | 7566 | 1982-12-09 00:00:00 | 3000 | NULL | 20 |
| 7876 | ADAMS | CLERK | 7788 | 1983-01-12 00:00:00 | 1100 | NULL | 20 |
+-------+-------+---------+------+---------------------+------+------+--------+
2 rows in set (0.00 sec)
mysql> select * from information_schema.index_statistics;
+--------------+------------+------------------+-----------+
| TABLE_SCHEMA | TABLE_NAME | INDEX_NAME | ROWS_READ |
+--------------+------------+------------------+-----------+
| test | emp | idx_date_sal_job | 3 |
+--------------+------------+------------------+-----------+
1 row in set (0.04 sec)
mysql> select * from emp;
+-------+--------+-----------+------+---------------------+------+------+--------+
| empno | ename | job | mgr | hiredate | sal | comm | deptno |
+-------+--------+-----------+------+---------------------+------+------+--------+
| 7369 | SMITH | CLERK | 7902 | 1980-12-17 00:00:00 | 800 | NULL | 20 |
| 7499 | ALLEN | SALESMAN | 7698 | 1981-02-20 00:00:00 | 1600 | 300 | 30 |
| 7521 | WARD | SALESMAN | 7698 | 1981-02-22 00:00:00 | 1250 | 500 | 30 |
| 7566 | JONES | MANAGER | 7839 | 1981-04-02 00:00:00 | 2975 | NULL | 20 |
| 7654 | MARTIN | SALESMAN | 7698 | 1981-09-28 00:00:00 | 1250 | 1400 | 30 |
| 7698 | BLAKE | MANAGER | 7839 | 1981-05-01 00:00:00 | 2850 | NULL | 30 |
| 7782 | CLARK | MANAGER | 7839 | 1981-06-09 00:00:00 | 2450 | NULL | 10 |
| 7788 | SCOTT | ANALYST | 7566 | 1982-12-09 00:00:00 | 3000 | NULL | 20 |
| 7839 | KING | PRESIDENT | NULL | 1981-11-17 00:00:00 | 5000 | NULL | 10 |
| 7844 | TURNER | SALESMAN | 7698 | 1981-09-08 00:00:00 | 1500 | 0 | 30 |
| 7876 | ADAMS | CLERK | 7788 | 1983-01-12 00:00:00 | 1100 | NULL | 20 |
| 7900 | JAMES | CLERK | 7698 | 1981-12-03 00:00:00 | 950 | NULL | 30 |
| 7902 | FORD | ANALYST | 7566 | 1981-12-03 00:00:00 | 3000 | NULL | 20 |
| 7934 | MILLER | CLERK | 7782 | 1982-01-23 00:00:00 | 1300 | NULL | 10 |
+-------+--------+-----------+------+---------------------+------+------+--------+
14 rows in set (0.00 sec)
mysql> select * from information_schema.index_statistics;
+--------------+------------+------------------+-----------+
| TABLE_SCHEMA | TABLE_NAME | INDEX_NAME | ROWS_READ |
+--------------+------------+------------------+-----------+
| test | emp | PRIMARY | 14 |
| test | emp | idx_date_sal_job | 3 |
+--------------+------------+------------------+-----------+
2 rows in set (0.00 sec)
mysql> select * from emp where hiredate > '1982-01-01' and deptno = 20;
+-------+-------+---------+------+---------------------+------+------+--------+
| empno | ename | job | mgr | hiredate | sal | comm | deptno |
+-------+-------+---------+------+---------------------+------+------+--------+
| 7788 | SCOTT | ANALYST | 7566 | 1982-12-09 00:00:00 | 3000 | NULL | 20 |
| 7876 | ADAMS | CLERK | 7788 | 1983-01-12 00:00:00 | 1100 | NULL | 20 |
+-------+-------+---------+------+---------------------+------+------+--------+
2 rows in set (0.00 sec)
mysql> select * from emp;
+-------+--------+-----------+------+---------------------+------+------+--------+
| empno | ename | job | mgr | hiredate | sal | comm | deptno |
+-------+--------+-----------+------+---------------------+------+------+--------+
| 7369 | SMITH | CLERK | 7902 | 1980-12-17 00:00:00 | 800 | NULL | 20 |
| 7499 | ALLEN | SALESMAN | 7698 | 1981-02-20 00:00:00 | 1600 | 300 | 30 |
| 7521 | WARD | SALESMAN | 7698 | 1981-02-22 00:00:00 | 1250 | 500 | 30 |
| 7566 | JONES | MANAGER | 7839 | 1981-04-02 00:00:00 | 2975 | NULL | 20 |
| 7654 | MARTIN | SALESMAN | 7698 | 1981-09-28 00:00:00 | 1250 | 1400 | 30 |
| 7698 | BLAKE | MANAGER | 7839 | 1981-05-01 00:00:00 | 2850 | NULL | 30 |
| 7782 | CLARK | MANAGER | 7839 | 1981-06-09 00:00:00 | 2450 | NULL | 10 |
| 7788 | SCOTT | ANALYST | 7566 | 1982-12-09 00:00:00 | 3000 | NULL | 20 |
| 7839 | KING | PRESIDENT | NULL | 1981-11-17 00:00:00 | 5000 | NULL | 10 |
| 7844 | TURNER | SALESMAN | 7698 | 1981-09-08 00:00:00 | 1500 | 0 | 30 |
| 7876 | ADAMS | CLERK | 7788 | 1983-01-12 00:00:00 | 1100 | NULL | 20 |
| 7900 | JAMES | CLERK | 7698 | 1981-12-03 00:00:00 | 950 | NULL | 30 |
| 7902 | FORD | ANALYST | 7566 | 1981-12-03 00:00:00 | 3000 | NULL | 20 |
| 7934 | MILLER | CLERK | 7782 | 1982-01-23 00:00:00 | 1300 | NULL | 10 |
+-------+--------+-----------+------+---------------------+------+------+--------+
14 rows in set (0.00 sec)
mysql> select * from information_schema.index_statistics;
+--------------+------------+------------------+-----------+
| TABLE_SCHEMA | TABLE_NAME | INDEX_NAME | ROWS_READ |
+--------------+------------+------------------+-----------+
| test | emp | PRIMARY | 28 |
| test | emp | idx_date_sal_job | 6 |
+--------------+------------+------------------+-----------+
2 rows in set (0.00 sec)
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