Question

I have a table of user-generated content that includes an ENUM format column for status. (Pending, Approved, Approved-auto, or Rejected) To keep en eye on the amount of recent content by status, I use the following query:

mysql> SELECT DATE(dt_submitted) AS date, 
              COUNT(*) AS count,
              SUM(IF(status='Approved', 1, 0)) as approved,
              SUM(IF(status='Approved-auto', 1, 0)) as approved_auto,
              SUM(IF(status='Rejected', 1, 0)) as rejected,
              SUM(IF(status='Pending', 1, 0)) as pending
       FROM post
       WHERE dt_submitted > DATE_SUB(CURDATE(), INTERVAL 30 DAY)
       GROUP BY date;
+------------+-------+----------+---------------+----------+---------+
| date       | count | approved | approved_auto | rejected | pending |
+------------+-------+----------+---------------+----------+---------+
| 2011-11-22 |   131 |      124 |             0 |        7 |       0 | 
| 2011-11-23 |   116 |      114 |             0 |        2 |       0 | 
...
| 2011-12-21 |   690 |      674 |             5 |       11 |       0 | 
| 2011-12-22 |    80 |       75 |             0 |        4 |      38 | 
+------------+-------+----------+---------------+----------+---------+
31 rows in set (0.60 sec)

This is nearly perfect, but I’m picky and want to see if I can make it faster. (0.6 sec is slow on this server, and the table changes too often to worry about passing a static date to cache results.)

If I EXPLAIN the query, it’s not using any indexes (status is indexed). (Is this because it’s referring to the temporary table created for the SUMs?)

explain SELECT DATE(dt_submitted) AS date, COUNT(*) AS count, SUM(IF(status='Approved', 1, 0)) as approved, SUM(IF(status='Approved-auto', 1, 0)) as approved_auto, SUM(IF(status='Rejected', 1, 0)) as rejected, SUM(IF(status='Pending', 1, 0)) as pending FROM post WHERE dt_submitted > DATE_SUB(CURDATE(), INTERVAL 30 DAY)  GROUP BY date;
+----+-------------+-------+------+---------------+------+---------+------+--------+----------------------------------------------+
| id | select_type | table | type | possible_keys | key  | key_len | ref  | rows   | Extra                                        |
+----+-------------+-------+------+---------------+------+---------+------+--------+----------------------------------------------+
|  1 | SIMPLE      | post  | ALL  | NULL          | NULL | NULL    | NULL | 529902 | Using where; Using temporary; Using filesort | 
+----+-------------+-------+------+---------------+------+---------+------+--------+----------------------------------------------+
1 row in set (0.00 sec)

So is there anything I can do to optimize the table or rewrite the query to make this faster? Or is this query simply limited by the speed of available system resources?

EDIT: dt_submitted was not indexed.

Answer 1

Double check that the appropriate columns are indexed.

(As noted in the edit, I failed to double-check my indexes. Once I indexed the appropriate column, the problem was solved.)