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    <p>Sometimes it is not the query itself which causes a slowdown - another query operating on the table can easily cause inserts to slow down due to transactional isolation and locking. Your slow queries might simply have been waiting for another transaction(s) to complete. This is fairly common on a busy table, or if your server is executing long/complex transactions.</p> <p>Another significant factor will be the overall performance of your database: how your <code>my.cnf</code> file is tuned, how the server itself is tuned, what else the server has running on it, and of course, what hardware the server is running.</p> <p>The linux tool <code>mytop</code> and the query <code>SHOW ENGINE INNODB STATUS\G</code> can be helpful to see possible trouble spots. General linux performance tools can also show how busy your disks are, etc.</p> <p>Given the nature of this table, have you considered an alternative way to keep track of who is online? In MySQL, I have used a <code>MEMORY</code> table for such purposes in the past. A NoSQL data store might also be good for this type of information. Redis could store this as a sorted set with much success (score == timestamp).</p> <p>Further reading:</p> <ul> <li><a href="http://dev.mysql.com/doc/refman/5.1/en/innodb-tuning.html" rel="nofollow noreferrer">http://dev.mysql.com/doc/refman/5.1/en/innodb-tuning.html</a></li> <li><a href="http://dev.mysql.com/doc/refman/5.1/en/memory-storage-engine.html" rel="nofollow noreferrer">http://dev.mysql.com/doc/refman/5.1/en/memory-storage-engine.html</a></li> <li><a href="http://redis.io/commands#sorted_set" rel="nofollow noreferrer">http://redis.io/commands#sorted_set</a></li> </ul>
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    1. COI added the following to my mysql config it should gain me some more performance. We will see. innodb_flush_log_at_trx_commit=0 innodb_support_xa=0 innodb_buffer_pool_size=536870912
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    2. COBtw i can't use the memory engine, because i need to have the online data in some persistent way, for later analysis.
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    3. CO@Kalkin: That sounds like an excuse to me - "business requirements demand it." Sometimes overly broad business requirements need to be re-evaluated in the face of technical hurdles. I'd advising re-thinking your requirements based on what you actually need to know. But overall, my post is about: don't just look at this one query, look at everything your database is doing. We don't know what that is, so we can only help so much.
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