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  1. MDEV-6935

Change the default value for innodb_log_compressed_pages to false



      commit ca40b4417fd224a68de6636b58c92f133703fc68

      Change the default value for innodb_log_compressed_pages to false

      Feature: 2012 InnoDB Compression

      Logging these pages is a waste. We don't want this to be enabled.

      One caution here: If the zlib version used by innodb is changed, but
      the running version is still the previous version, and the running
      version crashes, it is possible crash recovery could fail.

      When crash recovery uses a zlib version at all different than the
      version used by the crashed instance, it is possible that a redone
      compression could fail, where the original did not, because the new
      zlib version compresses the same data to a slightly larger size.

      Because of the nature of compression, this is even possible when
      upgrading to a version of zlib which actually peforms overall better
      compression than the previous version.

      If this happens, mysql will fail to recover, since a page split can
      not be safely triggered during crash recovery.

      So, either the exact zlib version must be controlled between builds,
      or these rare recovery failures must be accepted. The cost of
      logging these pages is quite high, so we consider this limitation to
      be worthwhile.

      This failure scenario can not happen if there was a clean shutdown.
      This is only relevant to restarting crashed instances, or starting an
      instance built via a hot backup too (XtraBackup).


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              • Assignee:
                jplindst Jan Lindström
                jplindst Jan Lindström
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