Hi,
I am trying to optimize the following query:
SELECT articles.* FROM articles INNER JOIN newsletters ON
articles.newsletter_id = newsletters.id INNER JOIN users ON users.id =
newsletters.user_id WHERE users.id =12 AND MONTH(articles.created_at) = '12'
AND DAY(articles.created_at) = '5' ORDER BY YEAR(articles.created_at),
LENGTH(articles.body);
I am trying to retrieve all the articles created on a specific day of a
specific month that belong to a user, ordered by the oldest and then longest
article.
I have run explain on the query, and get the following:
+----+-------------+----------+-------+------------------------------------------------------------------------+--------------------------------------------+---------+---------------------+------+----------------------------------------------+
| id | select_type | table | type |
possible_keys |
key | key_len | ref |
rows | Extra |
+----+-------------+----------+-------+------------------------------------------------------------------------+--------------------------------------------+---------+---------------------+------+----------------------------------------------+
| 1 | SIMPLE | users | const |
PRIMARY |
PRIMARY | 4 | const
| 1 | Using index; Using temporary; Using filesort |
| 1 | SIMPLE | newsletters | ref |
PRIMARY,index_newsletters_on_user_id |
index_newsletters_on_user_id | 4 |
const | 1 | Using index |
| 1 | SIMPLE | articles | ref |
index_articles_on_newsletter_id,index_articles_on_newsletter_id_and_created_at
| index_articles_on_newsletter_id_and_created_at | 4 |
my_db.newsletters.id | 3 | Using where |
+----+-------------+----------+-------+------------------------------------------------------------------------+--------------------------------------------+---------+---------------------+------+----------------------------------------------+
3 rows in set (0.00 sec)
This seems pretty decent, and does perform pretty well for some users (~0.5
- 1 sec), but for some users (seemingly those with large numbers of
articles) the query can take 20 - 30 seconds to run. This seems really slow
to me. I tried adding in the index
'index_articles_on_newsletter_id_and_created_at' but the performance doesn't
seem to be any different then when it uses just the
'index_articles_on_newsletter_id' index. I think this might be because of
the functions I am using on the created_at column to get the day and month
from it, making an index on created_at useless in this instance.
Running both an 'optimize table entries' and 'analyze table entries' also
didn't seem to have any real impact on the performance.
I was wondering if anybody had any suggestions for what else I might be able
to try, or if there is a better way to search on dates in this manner. Any
ideas would be greatly appreciated.
Thanks,
Simon
