Enabling Automatic Configuration for a Dedicated MySQL Server ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 Note A  MERGE_THRESHOLD  value defined at the index level takes priority over a MERGE_THRESHOLD  value defined for the table. If undefined,  MERGE_THRESHOLD defaults to 50% ( MERGE_THRESHOLD=50 , which is the previously hardcoded value. Likewise, you can use  SHOW INDEX  to view the  MERGE_THRESHOLD  value for an index, if explicitly defined using the  index_option COMMENT  clause: mysql>  SHOW INDEX FROM t2 \G *************************** 1. row *************************** Table: t2 Non_unique: 1 Key_name: id_index  Seq_in_index: 1 Column_name: id Collation: A Cardinality: 0 Sub_part: NULL Packed: NULL Null: YES Index_type: BTREE Comment: Index_comment: MERGE_THRESHOLD=40 mysql>  SELECT NAME, COMMENT FROM INFORMATION_SCHEMA.INNODB_METRICS WHERE NAME like ’%index_page_merge%’; +-----------------------------+----------------------------------------+ | NAME | COMMENT | +-----------------------------+----------------------------------------+ | index_page_merge_attempts | Number of index page merge attempts | | index_page_merge_successful | Number of successful index page merges | +-----------------------------+----------------------------------------+ 3144 15.8.12 Enabling Automatic Configuration for a Dedicated MySQL Server When lowering the  MERGE_THRESHOLD  value, the objectives are: A  MERGE_THRESHOLD  setting that is too small could result in large data files due to an excessive amount of empty page space. For information about using  INNODB_METRICS  counters, see Section 15.15.6, “InnoDB INFORMATION_SCHEMA Metrics Table” . When  innodb_dedicated_server  is enabled,  InnoDB  automatically configures the following variables: • innodb_log_files_in_group  (as of MySQL 8.0.14) • innodb_log_file_size • innodb_buffer_pool_size •A similar number of page merge attempts and successful page merges •A smaller number of page merge attempts and successful page merges Measuring the Effect of MERGE_THRESHOLD Settings The  INNODB_METRICS  table provides two counters that can be used to measure the effect of a MERGE_THRESHOLD  setting on index page merges.