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Enabling this option causes MySQL to write DDL logs to stderr . For more information, see Viewing DDL Logs. 

• innodb_purge_batch_size 

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Defines the number of undo log pages that purge parses and processes in one batch from the history list. In a multithreaded purge configuration, the coordinator purge thread divides innodb_purge_batch_size  by innodb_purge_threads  and assigns that number of pages to each purge thread. The innodb_purge_batch_size  variable also defines the number of undo log pages that purge frees after every 128 iterations through the undo logs. 

The innodb_purge_batch_size  option is intended for advanced performance tuning in combination with the innodb_purge_threads  setting. Most users need not change innodb_purge_batch_size from its default value. 

For related information, see Section 15.8.9, “Purge Configuration” . 

• innodb_purge_threads 

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