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  1. Percona Toolkit
  2. PT-804

LP #1258135: pt-deadlock-logger introduces a noise to MySQL

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      **Reported in Launchpad by Roman Vynar last update 10-07-2014 12:12:31

      Hello,

      pt-deadlock-logger introduces a noise to MySQL because it does:
      INSERT IGNORE INTO `percona`.`deadlocks` (`server`,`ts`,`thread`,`txn_id`,`txn_time`,`user`,`hostname`,`ip`,`db`,`tbl`,`idx`,`lock_type`,`lock_mode`,`wait_hold`,`victim`,`query`)
      VALUES ...

      every minute on every deadlock that appears under SHOW ENGINE INNODB STATUS.

      For example, say a deadlock happened 1 year ago, and MySQL keeps it in the memory and pt-deadlock-logger will INSERT it into percona.deadlocks table every minute all the time until restart. This introduces a noise.
      If we expect to see no writes on the master, pt-deadlock-logger should not be a problem and should not introduce those unnecessary writes.

      The suggestion is to do SELECT to check whether a row exists in percona.deadlocks table and only do INSERT otherwise.

      Thanks.

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                lpjirasync lpjirasync (Inactive)
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