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POOptimizing an InnoDB table and a problematic query
 

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  1. POOptimizing an InnoDB table and a problematic query
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    <p>I have a biggish InnoDB table which at this moment contains about 20 million rows with ~20000 new rows inserted every day. They contain messages for different topics. </p> <pre><code>CREATE TABLE IF NOT EXISTS `Messages` ( `ID` bigint(20) unsigned NOT NULL AUTO_INCREMENT, `TopicID` bigint(20) unsigned NOT NULL, `DATESTAMP` int(11) DEFAULT NULL, `TIMESTAMP` int(10) unsigned NOT NULL, `Message` mediumtext NOT NULL, `Checksum` varchar(50) DEFAULT NULL, `Nickname` varchar(80) NOT NULL, PRIMARY KEY (`ID`), UNIQUE KEY `TopicID` (`TopicID`,`Checksum`), KEY `DATESTAMP` (`DATESTAMP`), KEY `Nickname` (`Nickname`), KEY `TIMESTAMP` (`TIMESTAMP`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8 AUTO_INCREMENT=25195126 ; </code></pre> <p>NOTE: The Cheksum stores an MD5 checksum which prevents same messages inserted twice in the same topics. (nickname + timestamp + topicid + last 20 chars of message)</p> <p>The site I'm building has a newsfeed in which users can select to view newest messages from different Nicknames from different forums. The query is as follows:</p> <pre><code>SELECT Messages.ID AS MessageID, Messages.Message, Messages.TIMESTAMP, Messages.Nickname, Topics.ID AS TopicID, Topics.Title AS TopicTitle, Forums.Title AS ForumTitle FROM Messages JOIN FollowedNicknames ON FollowedNicknames.UserID = 'MYUSERID' JOIN Forums ON Forums.ID = FollowedNicknames.ForumID JOIN Subforums ON Subforums.ForumID = Forums.ID JOIN Topics ON Topics.SubforumID = Subforums.ID WHERE Messages.Nickname = FollowedNicknames.Nickname AND Messages.TopicID = Topics.ID AND Messages.DATESTAMP = '2013619' ORDER BY Messages.TIMESTAMP DESC </code></pre> <p>The TIMESTAMP contains an unix timestamp and DATESTAMP is simply a date generated from the unix timestamp for faster access via '=' operator instead of range scans with unix timestamps.</p> <p>The problem is, this query takes about 13 seconds ( or more ) unbuffered. That is of course unacceptable for the intented usage. Adding the DATESTAMP seemed to speed things up, but not by much. </p> <p>At this point, I don't really know what should I do. I've read about composite primary keys, but I am still unsure whether they would do any good and how to correctly implement one in this particular case.</p> <p>I know that using BIGINTs may be a little overkill, but do they affect that much? </p> <p>EXPLAIN:</p> <pre><code>+----+-------------+-----------------------+--------+---------------------------------------+------------+---------+-----------------------------------------------+------+----------------------------------------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-----------------------+--------+---------------------------------------+------------+---------+-----------------------------------------------+------+----------------------------------------------+ | 1 | SIMPLE | FollowedNicknames | ALL | UserID,ForumID,Nickname | NULL | NULL | NULL | 8 | Using where; Using temporary; Using filesort | | 1 | SIMPLE | Forums | eq_ref | PRIMARY | PRIMARY | 8 | database.FollowedNicknames.ForumiID | 1 | NULL | | 1 | SIMPLE | Messages | ref | TopicID,DATETIME,Nickname | Nickname | 242 | database.FollowedNicknames.Nickname | 15 | Using where | | 1 | SIMPLE | Topics | eq_ref | PRIMARY,SubforumID | PRIMARY | 8 | database.Messages.TopicID | 1 | NULL | | 1 | SIMPLE | Subforums | eq_ref | PRIMARY,ForumID | PRIMARY | 8 | database.Topics.SubforumID | 1 | Using where | +----+-------------+-----------------------+--------+---------------------------------------+------------+---------+-----------------------------------------------+------+----------------------------------------------+ </code></pre>
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    1. PTQuestion
    1. USHenri Ruutinen
    1. USHenri Ruutinen
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    1. This table or related slice is empty.
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      1. PTAnswer
    1. This table or related slice is empty.
    1. COWhat does `EXPLAIN` suggest? http://dev.mysql.com/doc/refman/5.0/en/explain.html
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      1. POOptimizing an InnoDB table and a problematic query
      1. USdash
    2. COOutput of EXPLAIN added.
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      1. POOptimizing an InnoDB table and a problematic query
      1. USHenri Ruutinen
 

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