I am trying to avoid filesort but not getting luck in removing it from inner query. If I move condition to outer query then it shows me nothing.
Create table articles (
article_id Int UNSIGNED NOT NULL AUTO_INCREMENT,
editor_id Int UNSIGNED NOT NULL,
published_date Datetime,
Primary Key (book_id)) ENGINE = InnoDB;
Create Index published_date_INX ON articles (published_date);
Create Index editor_id_INX ON articles (editor_id);
EXPLAIN SELECT article_id, article_date FROM articles AA INNER JOIN
(
SELECT article_id
FROM articles
WHERE editor_id=1
ORDER BY published_date DESC
LIMIT 100, 5
) ART USING (article_id);
+----+-------------+------------+--------+---------------+-----------+---------+----------------+--------+----------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+------------+--------+---------------+-----------+---------+----------------+--------+----------------+
| 1 | | PRIMARY | <derived2> | ALL | NULL | NULL | NULL NULL | 5 | |
| 1 | | PRIMARY | AA | eq_ref | PRIMARY | PRIMARY | 4 ART.article_id | 1 | |
| 2 | | DERIVED | articles | ALL | editor_id | editor_id | 5 | 114311 | Using filesort |
+----+-------------+------------+--------+---------------+-----------+---------+----------------+--------+----------------+
3 rows in set (30.31 sec)
Any suggestion how to remove filesort from this query?
Maybe you can try adding an index on editor_id, published_date
.
create index edpub_INX on articles (editor_id, published_date);
On your inner query:
SELECT article_id
FROM articles
WHERE editor_id=1
ORDER BY published_date DESC
LIMIT 100, 5
MySQL's query planner is probably thinking that filtering by editor_id
(using the index) and then ordering by published_date
is better than using published_date_INX
and then filtering by editor_id
. And query planner is probably right.
So, if you want to "help" on that specific query, create an index on editor_id, published_date
and see if it helps your query run faster.
The technical post webpages of this site follow the CC BY-SA 4.0 protocol. If you need to reprint, please indicate the site URL or the original address.Any question please contact:yoyou2525@163.com.