getting rid of filesort on WordPress MySQL query
- by Hans
An instance of WordPress that I manage goes down about once a day due to this monster MySQL query taking far too long:
SELECT SQL_CALC_FOUND_ROWS distinct wp_posts.*
FROM wp_posts
LEFT JOIN wp_term_relationships ON (wp_posts.ID = wp_term_relationships.object_id) LEFT JOIN wp_term_taxonomy ON wp_term_taxonomy.term_taxonomy_id = wp_term_relationships.term_taxonomy_id LEFT JOIN wp_ec3_schedule ec3_sch ON ec3_sch.post_id=id
WHERE 1=1 AND wp_posts.ID NOT IN ( SELECT tr.object_id
FROM wp_term_relationships AS tr INNER JOIN wp_term_taxonomy AS tt ON tr.term_taxonomy_id = tt.term_taxonomy_id
WHERE tt.taxonomy = 'category' AND tt.term_id IN ('1050') ) AND wp_posts.post_type = 'post' AND (wp_posts.post_status = 'publish') AND NOT EXISTS (SELECT *
FROM wp_term_relationships JOIN wp_term_taxonomy ON wp_term_taxonomy.term_taxonomy_id = wp_term_relationships.term_taxonomy_id
WHERE wp_term_relationships.object_id = wp_posts.ID AND wp_term_taxonomy.taxonomy = 'category' AND wp_term_taxonomy.term_id IN (533,3567) ) AND ec3_sch.post_id IS NULL GROUP BY wp_posts.ID ORDER BY wp_posts.post_date DESC LIMIT 0, 10;
What do I have to do to get rid of the very slow filesort? I would think that the multicolumn type_status_date index would be fast enough.
The EXPLAIN EXTENDED output is below.
+----+--------------------+-----------------------+--------+-----------------------------------+------------------+---------+---------------------------------------------------------------------------------+------+----------------------------------------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+--------------------+-----------------------+--------+-----------------------------------+------------------+---------+---------------------------------------------------------------------------------+------+----------------------------------------------+
| 1 | PRIMARY | wp_posts | ref | type_status_date | type_status_date | 124 | const,const | 7034 | Using where; Using temporary; Using filesort |
| 1 | PRIMARY | wp_term_relationships | ref | PRIMARY | PRIMARY | 8 | bwog_wordpress_w.wp_posts.ID | 373 | Using index |
| 1 | PRIMARY | wp_term_taxonomy | eq_ref | PRIMARY | PRIMARY | 8 | bwog_wordpress_w.wp_term_relationships.term_taxonomy_id | 1 | Using index |
| 1 | PRIMARY | ec3_sch | ref | post_id_index | post_id_index | 9 | bwog_wordpress_w.wp_posts.ID | 1 | Using where; Using index |
| 3 | DEPENDENT SUBQUERY | wp_term_taxonomy | range | PRIMARY,term_id_taxonomy,taxonomy | term_id_taxonomy | 106 | NULL | 2 | Using where |
| 3 | DEPENDENT SUBQUERY | wp_term_relationships | eq_ref | PRIMARY,term_taxonomy_id | PRIMARY | 16 | bwog_wordpress_w.wp_posts.ID,bwog_wordpress_w.wp_term_taxonomy.term_taxonomy_id | 1 | Using index |
| 2 | DEPENDENT SUBQUERY | tt | const | PRIMARY,term_id_taxonomy,taxonomy | term_id_taxonomy | 106 | const,const | 1 | |
| 2 | DEPENDENT SUBQUERY | tr | eq_ref | PRIMARY,term_taxonomy_id | PRIMARY | 16 | func,const | 1 | Using index |
+----+--------------------+-----------------------+--------+-----------------------------------+------------------+---------+---------------------------------------------------------------------------------+------+----------------------------------------------+
8 rows in set, 2 warnings (0.05 sec)
And CREATE TABLE:
CREATE TABLE `wp_posts` (
`ID` bigint(20) unsigned NOT NULL auto_increment,
`post_author` bigint(20) unsigned NOT NULL default '0',
`post_date` datetime NOT NULL default '0000-00-00 00:00:00',
`post_date_gmt` datetime NOT NULL default '0000-00-00 00:00:00',
`post_content` longtext NOT NULL,
`post_title` text NOT NULL,
`post_excerpt` text NOT NULL,
`post_status` varchar(20) NOT NULL default 'publish',
`comment_status` varchar(20) NOT NULL default 'open',
`ping_status` varchar(20) NOT NULL default 'open',
`post_password` varchar(20) NOT NULL default '',
`post_name` varchar(200) NOT NULL default '',
`to_ping` text NOT NULL,
`pinged` text NOT NULL,
`post_modified` datetime NOT NULL default '0000-00-00 00:00:00',
`post_modified_gmt` datetime NOT NULL default '0000-00-00 00:00:00',
`post_content_filtered` text NOT NULL,
`post_parent` bigint(20) unsigned NOT NULL default '0',
`guid` varchar(255) NOT NULL default '',
`menu_order` int(11) NOT NULL default '0',
`post_type` varchar(20) NOT NULL default 'post',
`post_mime_type` varchar(100) NOT NULL default '',
`comment_count` bigint(20) NOT NULL default '0',
`robotsmeta` varchar(64) default NULL,
PRIMARY KEY (`ID`),
KEY `post_name` (`post_name`),
KEY `type_status_date` (`post_type`,`post_status`,`post_date`,`ID`),
KEY `post_parent` (`post_parent`),
KEY `post_date` (`post_date`),
FULLTEXT KEY `post_related` (`post_title`,`post_content`)
)
