????????????μ??SQL??Ч???

????1??????explain??

???????SQL??????explain??????SQL???????????????????????filesort??????????????????rows????????????????

????rows<1000????????????Χ????

????rows??1000~1w?????????????????????????????????????????????????????1??????Σ???????????????????????????????????

????rows????1?????????????SQL?????????SQL?????db????????????????????У???????1С???Σ???

????rows??10w??????????????????????е?SQL??????????????????????????????????????

????explain SQL????????????????е????????????explain???????????????????????????????????????????????SQL????????????????SQL???????????????????????????????????explain**

????2??MySQL????????

??????????MySQL??????????????my.cnf?м???log_slow_queries??long_query_time???????????????????в???????????long_query_time??SQL???????Щ???log?????????????????explain???????

????3????????????

???????MySQL?????show processlist?????????е?SQL?????????????е??????????????????????MySQLЧ????????????????????????????kill???

????4????????

???????top/vmstat?????????????MySQL????????cpu????棬???????IO????

??????MySQL????????o??????????????????б?????????????

?????????????????????innodb????????棬??????myisam??myisam????????????????????д???????????д????????е??????????????????.??innodb???м??????????????????????????????????????????????????

??????????????????SQL???where??????????????Σ???????????????????????????????????????д??Ч??????????????????д??????????????????￡????????????????????