MySQL慢查询查找和调优测试
网络编程 2021-07-05 15:27www.168986.cn编程入门
MySQL慢查询查找和调优测试,接下来详细介绍,需要了解的朋友可以参考下
编辑 my.f或者my.ini文件,去除狼蚁网站SEO优化这几行代码的注释
log_slow_queries = /var/log/mysql/mysql-slow.log
long_query_time = 2
log-queries-not-using-indexes
这将使得慢查询和没有使用索引的查询被记录下来。
这样做之后,对mysql-slow.log文件执行tail -f命令,将能看到其中记录的慢查询和未使用索引的查询。
随便提取一个慢查询,执行explain
explain low_query
你将看到狼蚁网站SEO优化的结果
+----+-------------+---------------------+------+---------------+------+---------+------+------+-------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+---------------------+------+---------------+------+---------+------+------+-------------+
| 1 | SIMPLE | some_table | ALL | NULL | NULL | NULL | NULL | 166 | Using where |
+----+-------------+---------------------+------+---------------+------+---------+------+------+-------------+
注意上面的rows和key列。rows显示该查询影响了多少行记录,我们不想让这个值太大。key显示用了哪个索引,为NULL时表示查询未用任何索引。
如果想让查询更快,你或许需要为某些列增加索引
CREATE INDEX myapp_mytable_myfield_idx on myapp_mytable(myfield);
除了配置mysql配置文件来实现记录慢查询外,还有狼蚁网站SEO优化的方法可以记录慢查询
SELECT t.TABLE_SCHEMA AS `db`,
t.TABLE_NAME AS `table`,
s.INDEX_NAME AS `index name`,
s.COLUMN_NAME AS `FIELD name`,
s.SEQ_IN_INDEX `seq IN index`,
s2.max_columns AS `# cols`,
s.CARDINALITY AS `card`,
t.TABLE_ROWS AS `est rows`,
ROUND(((s.CARDINALITY / IFNULL(t.TABLE_ROWS, 0.01)) 100), 2) AS `sel %`
FROM INFORMATION_SCHEMA.STATISTICS s
INNER JOIN INFORMATION_SCHEMA.TABLES t ON s.TABLE_SCHEMA = t.TABLE_SCHEMA AND s.TABLE_NAME = t.TABLE_NAME
INNER JOIN (
SELECT TABLE_SCHEMA, TABLE_NAME, INDEX_NAME, MAX(SEQ_IN_INDEX) AS max_columns
FROM INFORMATION_SCHEMA.STATISTICS
WHERE TABLE_SCHEMA != 'mysql' GROUP BY TABLE_SCHEMA, TABLE_NAME, INDEX_NAME ) AS s2 ON s.TABLE_SCHEMA = s2.TABLE_SCHEMA AND s.TABLE_NAME = s2.TABLE_NAME AND s.INDEX_NAME = s2.INDEX_NAME
WHERE t.TABLE_SCHEMA != 'mysql' / Filter out the mysql system DB /
AND t.TABLE_ROWS > 10 / Only tables with some rows /
AND s.CARDINALITY IS NOT NULL / Need at least one non-NULL value in the field /
AND (s.CARDINALITY / IFNULL(t.TABLE_ROWS, 0.01)) < 1.00 / unique indexes are perfect anyway /
ORDER BY `sel %`, s.TABLE_SCHEMA, s.TABLE_NAME / DESC for best non-unique indexes /
LIMIT 10;
代码如下:
log_slow_queries = /var/log/mysql/mysql-slow.log
long_query_time = 2
log-queries-not-using-indexes
这将使得慢查询和没有使用索引的查询被记录下来。
这样做之后,对mysql-slow.log文件执行tail -f命令,将能看到其中记录的慢查询和未使用索引的查询。
随便提取一个慢查询,执行explain
代码如下:
explain low_query
你将看到狼蚁网站SEO优化的结果
+----+-------------+---------------------+------+---------------+------+---------+------+------+-------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+---------------------+------+---------------+------+---------+------+------+-------------+
| 1 | SIMPLE | some_table | ALL | NULL | NULL | NULL | NULL | 166 | Using where |
+----+-------------+---------------------+------+---------------+------+---------+------+------+-------------+
注意上面的rows和key列。rows显示该查询影响了多少行记录,我们不想让这个值太大。key显示用了哪个索引,为NULL时表示查询未用任何索引。
如果想让查询更快,你或许需要为某些列增加索引
CREATE INDEX myapp_mytable_myfield_idx on myapp_mytable(myfield);
除了配置mysql配置文件来实现记录慢查询外,还有狼蚁网站SEO优化的方法可以记录慢查询
代码如下:
SELECT t.TABLE_SCHEMA AS `db`,
t.TABLE_NAME AS `table`,
s.INDEX_NAME AS `index name`,
s.COLUMN_NAME AS `FIELD name`,
s.SEQ_IN_INDEX `seq IN index`,
s2.max_columns AS `# cols`,
s.CARDINALITY AS `card`,
t.TABLE_ROWS AS `est rows`,
ROUND(((s.CARDINALITY / IFNULL(t.TABLE_ROWS, 0.01)) 100), 2) AS `sel %`
FROM INFORMATION_SCHEMA.STATISTICS s
INNER JOIN INFORMATION_SCHEMA.TABLES t ON s.TABLE_SCHEMA = t.TABLE_SCHEMA AND s.TABLE_NAME = t.TABLE_NAME
INNER JOIN (
SELECT TABLE_SCHEMA, TABLE_NAME, INDEX_NAME, MAX(SEQ_IN_INDEX) AS max_columns
FROM INFORMATION_SCHEMA.STATISTICS
WHERE TABLE_SCHEMA != 'mysql' GROUP BY TABLE_SCHEMA, TABLE_NAME, INDEX_NAME ) AS s2 ON s.TABLE_SCHEMA = s2.TABLE_SCHEMA AND s.TABLE_NAME = s2.TABLE_NAME AND s.INDEX_NAME = s2.INDEX_NAME
WHERE t.TABLE_SCHEMA != 'mysql' / Filter out the mysql system DB /
AND t.TABLE_ROWS > 10 / Only tables with some rows /
AND s.CARDINALITY IS NOT NULL / Need at least one non-NULL value in the field /
AND (s.CARDINALITY / IFNULL(t.TABLE_ROWS, 0.01)) < 1.00 / unique indexes are perfect anyway /
ORDER BY `sel %`, s.TABLE_SCHEMA, s.TABLE_NAME / DESC for best non-unique indexes /
LIMIT 10;
编程语言
- 甘肃哪有关键词排名优化购买方式有哪些
- 甘肃SEO如何做网站优化
- 河南seo关键词优化怎么做电话营销
- 北京SEO优化如何做QQ群营销
- 来宾百度关键词排名:提升您网站曝光率的关键
- 卢龙关键词优化:提升您网站排名的策略与技巧
- 山东网站优化的注意事项有哪些
- 四川整站优化怎样提升在搜索引擎中的排名
- 疏附整站优化:提升网站性能与用户体验的全新
- 海南seo主要做什么工作售后服务要做到哪些
- 荣昌百度网站优化:提升您网站的搜索引擎排名
- 河北seo网站排名关键词优化如何做SEO
- 江西优化关键词排名推广售后保障一般有哪些
- 古浪SEO优化:提升你的网站可见性
- 西藏网站排名优化怎么把网站排名在百度首页
- 如何提升阳东百度快照排名:详尽指南