[英]MySQL slow avg min max using filesort
我如何优化查询,它已经花费了大约2秒钟的时间,并且在“结果”表中有大约50万条记录,但是我希望这个麻烦会增长到数十亿。
SELECT
hopcount, hop, round( avg( rtt ) , 2 ) AS avg, min( rtt ) AS min, max( rtt ) AS max
FROM results
JOIN traces ON id = trace
WHERE target =9
AND rtt > -1
GROUP BY hop`
解释输出:
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE traces ref PRIMARY,fk_traces_1_idx fk_traces_1_idx 5 const 26333 Using where; Using temporary; Using filesort
1 SIMPLE results ref trace trace 5 pinger.traces.id 7 Using where
表格:
CREATE TABLE IF NOT EXISTS `results` (
`hop` int(11) DEFAULT NULL,
`trace` int(11) DEFAULT NULL,
`rtt` int(11) NOT NULL,
`seq` int(11) NOT NULL,
KEY `trace` (`trace`),
KEY `fk_hops_id` (`hop`),
KEY `seq` (`seq`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
CREATE TABLE IF NOT EXISTS `traces` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`time` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
`hopcount` smallint(6) NOT NULL,
`target` int(11) DEFAULT NULL,
PRIMARY KEY (`id`),
KEY `fk_traces_1_idx` (`target`,`id`,`time`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 AUTO_INCREMENT=52308;
在MySQL中, GROUP BY
表示ORDER BY
要删除此隐式排序,请添加ORDER BY NULL
如果使用GROUP BY,则输出行将根据GROUP BY列进行排序,就好像您对同一列使用ORDER BY一样。 为避免GROUP BY产生的排序开销,请添加ORDER BY NULL:
而且在ORDER BY优化中
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