Re: Slow SQL query

> Den 27/10/2014 kl. 13.20 skrev Collin Anderson <cmawebsite@gmail.com>:
>
> mysql> explain SELECT COUNT(*)
> -> FROM `order_order`
> -> WHERE `order_order`.`status` != 4
> -> AND (`order_order`.`user_id` = 12345 OR `order_order`.`account_number`
> -> = 123456);
> +----+-------------+-------------+------+-------------------------------------------------------------------------------------+------+---------+------+--------+-------------+
> | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
> +----+-------------+-------------+------+-------------------------------------------------------------------------------------+------+---------+------+--------+-------------+
> | 1 | SIMPLE | order_order | ALL | order_order_fbfc09f1,order_order_979d4f1e,order_order_48fb58bb,order_order_309e75c7 | NULL | NULL | NULL | 338275 | Using where |
> +----+-------------+-------------+------+-------------------------------------------------------------------------------------+------+---------+------+--------+-------------+
> 1 row in set (0.16 sec)
>
> I can't get it to use the indexes when I have the "status" clause.

Note that your indexes are on individual columns, not combined. So MySQL has to choose one of the indexes; it can't combine them. It's probably choosing the state index, then deciding that the cardinality is very low (or stats show that state=4 is true for more than n pct of the rows) and then does a full table scan.

You might benefit from adding combined indexes with status and account_number|user.

class Meta:
index_together = [
['status', 'account_number'],
['status', 'user'],
]


Erik

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