我正在尝试获取相对主题标签。
我在标签和帖子表之间有很多关系。
例如,对于主题标签"爱",我尝试获取他们发布的所有主题标签都有Love
主题标签。
这是我的查询(标签67是"爱"(
SELECT hashtag_id, count(hashtag_id) as count
from post_hashtag
where
# where posts has hashtag '67'
post_id in ( SELECT post_id FROM post_hashtag WHERE hashtag_id = 67 )
# remove hashtag 67 from result
and hashtag_id != 67
# group them and sort by count, so the must repeated hashtag is the best relative hashtag
GROUP by hashtag_id
ORDER by count desc
limit 4
我尝试优化我的查询,但我无法进一步优化它(目前根据帖子数量需要 2 - 12 秒(
有没有办法优化它?
解释查询
+----+-------------+-----------------+------------+--------+---------------+---------------------------------------------------+---------+-------------------------------------------+---------+----------+-------------+
| id | select_type | table | partitions | type | possible_keys | key | key_len | ref | rows | filtered | Extra |
+----+-------------+-----------------+------------+--------+---------------+---------------------------------------------------+---------+-------------------------------------------+---------+----------+-------------+
| 1 | SIMPLE | post_hashtag | NULL | index | NULL | fk_np_account_post_has_np_hashtag_np_hashtag1_idx | 4 | NULL | 4623584 | 100.00 | Using index |
| 1 | SIMPLE | hashtag | NULL | eq_ref | PRIMARY | PRIMARY | 4 | graphicj_novin.np_post_hashtag.hashtag_id | 1 | 100.00 | NULL |
+----+-------------+-----------------+------------+--------+---------------+---------------------------------------------------+---------+-------------------------------------------+---------+----------+-------------+
post_hashtag
有这些字段
post_id,hashtag_id
两个字段都是外键
MySQL通常优化WHERE IN (SELECT ...)
很差。请改用JOIN
。
SELECT p1.hashtag_id, count(*) as count
from post_hashtag AS p1
JOIN post_hashtag AS p2 ON p1.post_id = p2.post_id
WHERE p1.hashtag_id != 67
AND p2.hashtag_id = 67
GROUP by p1.hashtag_id
ORDER by count desc
limit 4