即使我查询的所有字段都已编入索引，但我的查询执行时间太长（4秒）。以下是查询和解释结果。有什么想法是什么问题？ （执行查询时，mysql CPU使用率最高可达100％
EXPLAIN SELECT count(hd.did) as NumPo, `hd`.`sid`, `src`.`Name`
FROM (`hd`)
JOIN `result` ON `result`.`did` = `hd`.`did`
JOIN `sf` ON `sf`.`fid` = `hd`.`fid`
JOIN `src` ON `src`.`sid` = `hd`.`sid`
WHERE `sf`.`tid` = 2
AND `result`.`set` = 'xxxxxxx'
GROUP BY `hd`.`sid`
ORDER BY `NumPo` DESC
LIMIT 10;
+----+-------------+--------------+--------+-------------------------+---------+---------+--------------------------+------+----------------------------------------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+--------------+--------+-------------------------+---------+---------+--------------------------+------+----------------------------------------------+
| 1 | SIMPLE | sf | ref | PRIMARY,type | type | 2 | const | 4 | Using index; Using temporary; Using filesort |
| 1 | SIMPLE | hd | ref | PRIMARY,sid,fid | FeedID | 4 | f2.sf.fid | 3 | |
| 1 | SIMPLE | result | ALL | resultset | NULL | NULL | NULL | 5322 | Using where; Using join buffer |
| 1 | SIMPLE | src | eq_ref | PRIMARY | PRIMARY | 4 | f2.hd.sid | 1 | |
+----+-------------+--------------+--------+-------------------------+---------+---------+--------------------------+------+----------------------------------------------+
答案 0 :(得分：3)
| 1 | SIMPLE | result | ALL | resultset | NULL | NULL | NULL | 5322 | Using where; Using join buffer |
看起来它没有在最大的表上使用索引。我无法猜测这个查询应该做什么，但看起来你在result.set上有一个索引，所以我尝试在result.did添加一个，看看是否有帮助。