Question

我正在使用MU wordpress网站，我在查询中遇到问题需要花费太多时间才能执行。

SELECT wp_posts.* FROM wp_posts 
INNER JOIN wp_term_relationships ON (wp_posts.ID = wp_term_relationships.object_id) 
INNER JOIN wp_term_taxonomy ON (wp_term_relationships.term_taxonomy_id = wp_term_taxonomy.term_taxonomy_id) 
INNER JOIN wp_terms ON (wp_term_taxonomy.term_id = wp_terms.term_id) 
WHERE 1=1 AND wp_posts.blog_id = '1'
AND wp_term_taxonomy.taxonomy = 'post_tag' 
AND wp_terms.slug IN ('rate') 
AND wp_posts.post_type = 'post' 
AND (wp_posts.post_status = 'publish') 
GROUP BY wp_posts.ID 
ORDER BY wp_posts.post_date DESC 
LIMIT 0, 20

这个由wordpress执行的查询执行需要30-40秒，这太多了。

wp_posts：4,00,000行
wp_terms：2,50,000行
wp_term_relationship：2,30,000行
wp_term_taxonomy：2,60,000行

我已将列（已使用）编入索引。

Answer 1

尝试并解释如下。

将以下内容粘贴到phpmyadmin并执行它： -

EXPLAIN SELECT wp_posts.* FROM wp_posts 
INNER JOIN wp_term_relationships ON (wp_posts.ID = wp_term_relationships.object_id) 
INNER JOIN wp_term_taxonomy ON (wp_term_relationships.term_taxonomy_id = wp_term_taxonomy.term_taxonomy_id) 
INNER JOIN wp_terms ON (wp_term_taxonomy.term_id = wp_terms.term_id) 
WHERE 1=1 AND wp_posts.blog_id = '1'
AND wp_term_taxonomy.taxonomy = 'post_tag' 
AND wp_terms.slug IN ('rate') 
AND wp_posts.post_type = 'post' 
AND (wp_posts.post_status = 'publish') 
GROUP BY wp_posts.ID 
ORDER BY wp_posts.post_date DESC 
LIMIT 0, 20

然后复制该结果并将其粘贴到原始问题中。它将详细说明在哪些表等中使用了哪些键

Answer 2

将来，您可以随时重新编辑帖子并添加内容，例如转储EXPLAIN（sql语句），而不是转储到评论中。

查询本身看起来非常直接，并且每个解释的索引都显示正常，但对于WP_Posts表，我可能会根据

更改（或只添加另一个索引）

( Blog_ID, Post_Type, Post_Status, ID, Post_Date )

这样，它首先匹配条件，然后匹配优化GROUP BY的ID，最后匹配Order By子句的Post_Date。

接下来，首先引擎不会尝试使用其他参考表，您是否尝试过添加关键字“STRAIGHT_JOIN”...

SELECT STRAIGHT_JOIN wp_posts.* ... rest of query

我要考虑的另一个替代方案是通过distinct预先查询ID，然后再联接回WP_Posts表...我不知道它是否会阻塞你做SELECT *并仅通过ID进行分组。

SELECT
      wp_posts.* 
   FROM 
      ( SELECT STRAIGHT_JOIN DISTINCT 
              WP.ID
           from 
              wp_posts WP
                 INNER JOIN wp_term_relationships WPR
                    ON WP.ID = WPR.object_id
                    INNER JOIN wp_term_taxonomy WPTT
                       ON WPR.term_taxonomy_id = WPTT.term_taxonomy_id
                       INNER JOIN wp_terms WPT
                          ON WPTT.term_id = WPT.term_id
           WHERE 
                  1 = 1 
              AND WP.blog_id = '1'
              AND WP.post_type = 'post' 
              AND WP.post_status = 'publish'
              AND WPTT.taxonomy = 'post_tag' 
              AND WPT.slug IN ('rate') 
           GROUP BY 
              WP.ID 
           ORDER BY 
              WP.post_date DESC 
           LIMIT
              0, 20 ) JustIDs
      JOIN WP_Posts
         on JustIDs.ID = WP_Posts.ID

慢wordpress查询时间

2 个答案: