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POHow to optimize a count SQL query on a big table
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copied!<p>I have a big table on mysql (innodb) which contains products assets (13 millions of rows). Here a little schema of my database :</p> <pre><code>product <-many2one-- file_item --one2many--> family --many2one--> download_type </code></pre> <p>The *file_item* table is the big table with millions of rows. I try to count products by download types with the following sql query :</p> <pre><code>select t.name as type, count(p.product_id) as n from file_item p inner join family f on f.id = p.family_id inner join type t on f.id_type = t.id group by t.id order by t.name; </code></pre> <p>There are 3 indexes on *file_item* table:</p> <ul> <li>product_family_idx (product_id, family_id) </li> <li>family_idx (family_id) </li> <li>product_idx (product_id) Explain output :</li> </ul> <pre> +----+-------------+-------+--------+-----------------------------------+---------+---------+-------------------+----------+---------------------------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------+--------+-----------------------------------+---------+---------+-------------------+----------+---------------------------------+ | 1 | SIMPLE | p | ALL | FAMILY_IDX,PRODUCT_FAMILY_IDX | NULL | NULL | NULL | 13862870 | Using temporary; Using filesort | | 1 | SIMPLE | f | eq_ref | PRIMARY,TYPE_ID | PRIMARY | 4 | MEDIA.p.FAMILY_IDX| 1 | | | 1 | SIMPLE | t | eq_ref | PRIMARY | PRIMARY | 4 | MEDIA.f.TYPE_ID | 1 | | +----+-------------+-------+--------+-----------------------------------+---------+---------+-------------------+----------+---------------------------------+ </pre> <p>The query takes more than 1 hour to return the results. Please how I can optimize the query ?!</p>

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