Analyze Table 分析表 MySQL 的Optimizer(优化元件)在优化SQL语句时,首先需要收集一些相关信息,其中就包括表的cardinality(可以翻译为“散列程度”),它表示某个索引对应的列包含多少个不同的值——如果cardinality大大少于数据的实际散列程度,那么索引就基本失效了.我们可以使用SHOW INDEX语句来查看索引的散列程度: SHOW INDEX FROM PLAYERS; TABLE KEY_NAME COLUMN_NAME CARDINALI…
Configuration Inserting log requests into the application code requires a fair amount of planning and effort. Observation shows that approximately 4 percent of code is dedicated to logging. Consequently, even moderately sized applications will have t…