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POSerious MySQL Performance Issue (Joins, Temporary Table, Filesort....)
 

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    <p>I've got a users table and a votes table. The votes table stores votes toward other users. And for better or worse, a single row in the votes table, stores the votes in both directions between the two users.</p> <p>Now, the problem is when I wanna list for example all people someone has voted on.</p> <p>I'm no MySQL expert, but from what I've figured out, thanks to the OR condition in the join statement, it needs to look through the <em>whole</em> users table (currently +44,000 rows), and it creates a temporary table to do so.</p> <p>Currently, the bellow query takes about two minutes, yes, <strong>two minutes</strong> to complete. If I remove the OR condition, and everything after it in the join statement, it runs in less than half a second, as it only needs to look through about 17 of the 44,000 user rows (<em>explain</em> ftw!).</p> <p>The bellow example, the user ID is <em>9834</em>, and I'm trying to fetch his/her own <em>no</em> votes, and join the info from user who was voted on to the result.</p> <p>Is there a better, and faster way to do this query? Or should I restructure the tables? I seriously hope it can be fixed by modifying the query, cause there's already a lot of users (+44,000), and votes (+130,000) in the tables, which I'd have to migrate.</p> <p>thanks :)</p> <pre><code>SELECT *, votes.id as vote_id FROM `votes` LEFT JOIN users ON ( ( votes.user_id_1 = 9834 AND users.uid = votes.user_id_2 ) OR ( votes.user_id_2 = 9834 AND users.uid = votes.user_id_1 ) ) WHERE ( ( votes.user_id_1 = 9834 AND votes.vote_1 = 0 ) OR ( votes.user_id_2 = 9834 AND votes.vote_2 = 0 ) ) ORDER BY votes.updated_at DESC LIMIT 0, 10 </code></pre>
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