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MySQL数据库最优化的简单方法

Jun 07, 2016 pm 04:11 PM
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以下的文章主要介绍的是MySQL数据库最为简单实用的实际优化方法,其中包括MySQL InnoDB 性能问题讨论 ,MySQL数据库的性能优化 ,以下就是文章的具体内容的描述,希望会给你带来一些帮助在此方面。 1、定期分析表和检查表 分析表的语法如下: 引用 ANALYZE[L

以下的文章主要介绍的是MySQL数据库最为简单实用的实际优化方法,其中包括MySQL InnoDB 性能问题讨论 ,MySQL数据库的性能优化 ,以下就是文章的具体内容的描述,希望会给你带来一些帮助在此方面。

1、定期分析表和检查表

分析表的语法如下:

引用

<ol class="dp-xml"><li class="alt"><span><span>ANALYZE [LOCAL | NO_WRITE_TO_BINLOG] TABLE tb1_name[, tbl_name]...  </span></span></li></ol>

以上语句用于分析和存储表的关键字分布,分析的结果将可以使得系统得到准确的统计信息,使得SQL能够生成正确的执行计划。如果用户感觉实际执行计划并不是预期的执行计划,执行一次分析表可能会解决问题。在分析期间,使用一个读取锁定对表进行锁定。这对于MyISAM,DBD和InnoDB表有作用。

例如分析一个数据表

引用

<ol class="dp-xml"><li class="alt"><span><span>analyze table table_name  </span></span></li></ol>

检查表的语法如下:

引用

<ol class="dp-xml"><li class="alt"><span><span>CHECK TABLE tb1_name[,tbl_name]...[option]</span><span class="attribute">...option</span><span> = {QUICK | FAST | MEDIUM | EXTENDED | CHANGED}  </span></span></li></ol>

检查表的作用是检查一个或多个表是否有错误,CHECK TABLE 对MyISAM 和 InnoDB表有作用,对于MyISAM表,关键字统计数据被更新

CHECK TABLE 也可以检查视图是否有错误,比如在视图定义中被引用的表不存在。

2. 定期优化表

优化表的语法如下:

引用

OPTIMIZE [LOCAL | NO_WRITE_TO_BINLOG] TABLE tb1_name [,tbl_name]...

如果删除了表的一大部分,或者如果已经对含有可变长度行的表(含有 VARCHAR、BLOB或TEXT列的表)进行更多更改,则应使用OPTIMIZE TABLE命令来进行表优化。这个命令可以将表中的空间碎片进行合并,并且可以消除由于删除或者更新造成的空间浪费,但OPTIMIZE TABLE 命令只对MyISAM、 BDB 和InnoDB表起作用。

例如: optimize table table_name

注意: analyze、check、optimize执行期间将对表进行锁定,因此一定注意要在MySQL数据库不繁忙的时候执行相关的操作。

常用的SQL优化

我们在开发的时候常常用到的SQL语句,无非是INSERT、GROUPBY等等。对于这些SQL语句,我们怎么进行优化?

1. 大批量插入数据

当用load命令导入数据的时候,适当的设置可以提高导入的速度。

对于MyISAM存储引擎的表,可以通过如下方式快速的导入大量的数据

引用

<ol class="dp-xml">
<li class="alt"><span><span>ALTER TABLE tb1_name DISABLE KEYS;   </span></span></li>
<li><span>loading the data   </span></li>
<li class="alt"><span>ALTER TABLE tb1_name ENABLE KEYS;  </span></li>
</ol>

DISABLE KEYS 和 ENABLE KEYS 用来打开或者关闭MyISAM表非唯一索引的更新。在导入大量的数据到一个非空的MyISAM表时,通过设置这两个命令,可以提高导入的效率。

对于导入大量的数据到一个空的MyISAM表时,默认就是先导入数据然后才创建索引的,索引不用进行设置。

引用

<ol class="dp-xml"><li class="alt"><span><span>load data infile '/home/mysql/text_txt' into table text  </span></span></li></ol>

对于InnoDB类型的表,这种方式不能提高导入数据的效率,但也有几种针对InnoDB类型的表进行优化的方式。

1. 因为InnoDB类型的表式按照主键的顺序保存的,所以将导入的数据按照主键的顺序排序,可以有效提高导入数据的效率。

2. 在导入数据前执行 SET UNIQUE_CHECKS=0,关闭唯一性校验,在导入结束后执行SET UNIQUE_CHECKS=1,恢复唯一性校验,可以提高导入的效率。

3. 如果应用使用自动提交的方式,建议在导入前执行SET AUTOCOMMIT=0,关闭自动提交,导入结束后执行SET AUTOCOMMIT=1,打开自动提交,也可以提高导入效率。

优化INSERT语句

当进行数据INSERT的时候,可以考虑采用以下几种方式进行优化

1. 如果同时从一个客户插入很多行,尽量使用多个值表的INSERT语句,这种方式将大大缩短客户端与MySQL数据库的链接、关闭等消耗,使得效率比分开执行的单个INSERT语句快.

例如:

<ol class="dp-xml">
<li class="alt"><span><span>insert into test values(1,2)   </span></span></li>
<li><span>insert into test values(3,4)   </span></li>
<li class="alt"><span>insert into test values(5,6)  </span></li>
</ol>

将上面三句改为:insert into test values(1,2),(3,4),(5,6)......

2. 如果从不同客户插入很多行,能通过使用INSERT DELAYED 语句得到更高的速度。

DELAYED 的含义是让INSERT 语句马上执行,其实数据都被放在内存的队列中,并没有真正写入磁盘,这比每条语句分别插入要快得多;LOW_PRIORITY刚好相反,在所有其他用户对表的读写完后才进行插入。

3. 将索引文件和数据文件分在不同的磁盘上存放

4. 如果进行批量插入,可以增加bulk_insert_buffer_size变量值的方法来提高速度,但是,这只能对于MyISAM表使用。

5. 当从一个文本文件中装载一个表时,使用LOAD DATA INFILE。 这通常比使用很多insert语句快20倍左右。


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