Table of Contents
瓶颈
表结构
Home Database Mysql Tutorial 找到 MySQL 的瓶颈_MySQL

找到 MySQL 的瓶颈_MySQL

Jun 01, 2016 pm 01:07 PM

瓶颈

对于项目的最终瓶颈是什么,我想大多数程序员已经达成了共识,是数据库

不论你使用哪种数据库,问题似乎最终都会回到这里。

首先,我们来分析一下导致瓶颈的主要原因:

  1. 查询次数太多;
  2. 返回的结果集太大;
  3. 查询太复杂;
  4. 数据更新表锁,导致查询堵塞;
  5. 软硬件环境限制,如最大连接数限制、IO限制、硬件资源限制;

针对这些问题,又有那些应对方法呢?

  1. 减少和合并查询;
  2. 减少查询字段,使用 LIMIT 拆分为多次查询;
  3. 简化和拆分查询,优化索引;
  4. 优化数据库软件配置;
  5. 分布和缓存;

表结构

数据库表的结构,不仅仅能够决定数据表所占用的空间,对查询效率有着显著的影响。

选择精确合理的字段类型

选择合适的字段类型,是表设计的最基本要求。合适的类型,不仅能够减少表占用的空间,而且能增加查询效率。

举个例子,存储时间(0000-00-00 00:00:00),你会使用 Char(19) 还是 DATETIME 呢?

你应该并必须选择后者,因为 DATETIME 在 MySQL 中几乎等同于数字,可以方便的运算、比较大小、被索引,以及比字符型占用更小的空间,查询效率甩出使用字符型几条街。

在数据库的其他条件已经决定的条件下,表的尺寸越小,查询越快,这几乎是一条定理。

所以,在设计表的时候,应该吝啬的使用更精确的字段类型。

考虑扩展性

这涉及到了程序设计的范畴,但同样也是表设计重要的一方面。

如果你设计一个用户表,表中涉及到权限的管理,目前只有发帖、回帖、删帖三类权限,你会怎么设计?

你是会使用canPost、canReply、canDelete三个字段来标识权限,还是使用位运算方式用一个权限字段?

实际上没有谁对谁错,但是我认为第二种方式扩展性更好一点,如果需求更改,又增加3种权限,第一种方式需要修改程序和数据表,第二种方式只需要程序调整。

扩展性是表设计的一个重要考量,一定要留有余地,但也要避免过度设计。

选择合适的字段类型,是表设计的最基本要求。合适的类型,不仅能够减少表占用的空间,而且能增加查询效率。

两个表分别用

对于项目的最终瓶颈是什么,我想大多数程序员已经达成了共识,是数据库

不论你使用哪种数据库,问题似乎最终都会回到这里。

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