Percona 5.5定位未使用的索引

feelpurple發表於2018-02-05
索引
開啟userstat引數，然後讓MySQL執行一段時間。
之後可以在INFORMATION_SCHEMA.INDEX_STATISTICS表中查詢到索引的使用頻率。

  1. mysql> show global variables like '%users%';
  2. +---------------+-------+
  3. | Variable_name | Value |
  4. +---------------+-------+
  5. | userstat | OFF |
  6. +---------------+-------+
  7. 1 row in set (0.00 sec)

  9. mysql> select * from information_schema.index_statistics;
  10. Empty set (0.00 sec)

  12. mysql> set global userstat=1;
  13. Query OK, 0 rows affected (0.00 sec)

  15. mysql> show global variables like '%users%';
  16. +---------------+-------+
  17. | Variable_name | Value |
  18. +---------------+-------+
  19. | userstat | ON |
  20. +---------------+-------+
  21. 1 row in set (0.00 sec)

  23. mysql> select * from information_schema.index_statistics;
  24. Empty set (0.00 sec)

  26. mysql> explain select * from emp where hiredate > '1982-01-01' and deptno = 20;
  27. +----+-------------+-------+-------+---------------------------+------------------+---------+------+------+-------------+
  28. | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
  29. +----+-------------+-------+-------+---------------------------+------------------+---------+------+------+-------------+
  30. | 1 | SIMPLE | emp | range | idx_date_sal_job,idx_date | idx_date_sal_job | 4 | NULL | 3 | Using where |
  31. +----+-------------+-------+-------+---------------------------+------------------+---------+------+------+-------------+
  32. 1 row in set (0.00 sec)

  34. mysql> select * from information_schema.index_statistics;
  35. Empty set (0.00 sec)

  37. mysql> select * from emp where hiredate > '1982-01-01' and deptno = 20;
  38. +-------+-------+---------+------+---------------------+------+------+--------+
  39. | empno | ename | job | mgr | hiredate | sal | comm | deptno |
  40. +-------+-------+---------+------+---------------------+------+------+--------+
  41. | 7788 | SCOTT | ANALYST | 7566 | 1982-12-09 00:00:00 | 3000 | NULL | 20 |
  42. | 7876 | ADAMS | CLERK | 7788 | 1983-01-12 00:00:00 | 1100 | NULL | 20 |
  43. +-------+-------+---------+------+---------------------+------+------+--------+
  44. 2 rows in set (0.00 sec)

  46. mysql> select * from information_schema.index_statistics;
  47. +--------------+------------+------------------+-----------+
  48. | TABLE_SCHEMA | TABLE_NAME | INDEX_NAME | ROWS_READ |
  49. +--------------+------------+------------------+-----------+
  50. | test | emp | idx_date_sal_job | 3 |
  51. +--------------+------------+------------------+-----------+
  52. 1 row in set (0.04 sec)

  54. mysql> select * from emp;
  55. +-------+--------+-----------+------+---------------------+------+------+--------+
  56. | empno | ename | job | mgr | hiredate | sal | comm | deptno |
  57. +-------+--------+-----------+------+---------------------+------+------+--------+
  58. | 7369 | SMITH | CLERK | 7902 | 1980-12-17 00:00:00 | 800 | NULL | 20 |
  59. | 7499 | ALLEN | SALESMAN | 7698 | 1981-02-20 00:00:00 | 1600 | 300 | 30 |
  60. | 7521 | WARD | SALESMAN | 7698 | 1981-02-22 00:00:00 | 1250 | 500 | 30 |
  61. | 7566 | JONES | MANAGER | 7839 | 1981-04-02 00:00:00 | 2975 | NULL | 20 |
  62. | 7654 | MARTIN | SALESMAN | 7698 | 1981-09-28 00:00:00 | 1250 | 1400 | 30 |
  63. | 7698 | BLAKE | MANAGER | 7839 | 1981-05-01 00:00:00 | 2850 | NULL | 30 |
  64. | 7782 | CLARK | MANAGER | 7839 | 1981-06-09 00:00:00 | 2450 | NULL | 10 |
  65. | 7788 | SCOTT | ANALYST | 7566 | 1982-12-09 00:00:00 | 3000 | NULL | 20 |
  66. | 7839 | KING | PRESIDENT | NULL | 1981-11-17 00:00:00 | 5000 | NULL | 10 |
  67. | 7844 | TURNER | SALESMAN | 7698 | 1981-09-08 00:00:00 | 1500 | 0 | 30 |
  68. | 7876 | ADAMS | CLERK | 7788 | 1983-01-12 00:00:00 | 1100 | NULL | 20 |
  69. | 7900 | JAMES | CLERK | 7698 | 1981-12-03 00:00:00 | 950 | NULL | 30 |
  70. | 7902 | FORD | ANALYST | 7566 | 1981-12-03 00:00:00 | 3000 | NULL | 20 |
  71. | 7934 | MILLER | CLERK | 7782 | 1982-01-23 00:00:00 | 1300 | NULL | 10 |
  72. +-------+--------+-----------+------+---------------------+------+------+--------+
  73. 14 rows in set (0.00 sec)

  75. mysql> select * from information_schema.index_statistics;
  76. +--------------+------------+------------------+-----------+
  77. | TABLE_SCHEMA | TABLE_NAME | INDEX_NAME | ROWS_READ |
  78. +--------------+------------+------------------+-----------+
  79. | test | emp | PRIMARY | 14 |
  80. | test | emp | idx_date_sal_job | 3 |
  81. +--------------+------------+------------------+-----------+
  82. 2 rows in set (0.00 sec)

  84. mysql> select * from emp where hiredate > '1982-01-01' and deptno = 20;
  85. +-------+-------+---------+------+---------------------+------+------+--------+
  86. | empno | ename | job | mgr | hiredate | sal | comm | deptno |
  87. +-------+-------+---------+------+---------------------+------+------+--------+
  88. | 7788 | SCOTT | ANALYST | 7566 | 1982-12-09 00:00:00 | 3000 | NULL | 20 |
  89. | 7876 | ADAMS | CLERK | 7788 | 1983-01-12 00:00:00 | 1100 | NULL | 20 |
  90. +-------+-------+---------+------+---------------------+------+------+--------+
  91. 2 rows in set (0.00 sec)

  93. mysql> select * from emp;
  94. +-------+--------+-----------+------+---------------------+------+------+--------+
  95. | empno | ename | job | mgr | hiredate | sal | comm | deptno |
  96. +-------+--------+-----------+------+---------------------+------+------+--------+
  97. | 7369 | SMITH | CLERK | 7902 | 1980-12-17 00:00:00 | 800 | NULL | 20 |
  98. | 7499 | ALLEN | SALESMAN | 7698 | 1981-02-20 00:00:00 | 1600 | 300 | 30 |
  99. | 7521 | WARD | SALESMAN | 7698 | 1981-02-22 00:00:00 | 1250 | 500 | 30 |
  100. | 7566 | JONES | MANAGER | 7839 | 1981-04-02 00:00:00 | 2975 | NULL | 20 |
  101. | 7654 | MARTIN | SALESMAN | 7698 | 1981-09-28 00:00:00 | 1250 | 1400 | 30 |
  102. | 7698 | BLAKE | MANAGER | 7839 | 1981-05-01 00:00:00 | 2850 | NULL | 30 |
  103. | 7782 | CLARK | MANAGER | 7839 | 1981-06-09 00:00:00 | 2450 | NULL | 10 |
  104. | 7788 | SCOTT | ANALYST | 7566 | 1982-12-09 00:00:00 | 3000 | NULL | 20 |
  105. | 7839 | KING | PRESIDENT | NULL | 1981-11-17 00:00:00 | 5000 | NULL | 10 |
  106. | 7844 | TURNER | SALESMAN | 7698 | 1981-09-08 00:00:00 | 1500 | 0 | 30 |
  107. | 7876 | ADAMS | CLERK | 7788 | 1983-01-12 00:00:00 | 1100 | NULL | 20 |
  108. | 7900 | JAMES | CLERK | 7698 | 1981-12-03 00:00:00 | 950 | NULL | 30 |
  109. | 7902 | FORD | ANALYST | 7566 | 1981-12-03 00:00:00 | 3000 | NULL | 20 |
  110. | 7934 | MILLER | CLERK | 7782 | 1982-01-23 00:00:00 | 1300 | NULL | 10 |
  111. +-------+--------+-----------+------+---------------------+------+------+--------+
  112. 14 rows in set (0.00 sec)

  114. mysql> select * from information_schema.index_statistics;
  115. +--------------+------------+------------------+-----------+
  116. | TABLE_SCHEMA | TABLE_NAME | INDEX_NAME | ROWS_READ |
  117. +--------------+------------+------------------+-----------+
  118. | test | emp | PRIMARY | 28 |
  119. | test | emp | idx_date_sal_job | 6 |
  120. +--------------+------------+------------------+-----------+
  121. 2 rows in set (0.00 sec)


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