Configuring the Merge Threshold for Index Pages ALTER TABLE t1 COMMENT=’MERGE_THRESHOLD=40’; To set the  MERGE_THRESHOLD  value for an individual index, you can use the  index_option COMMENT clause with  CREATE TABLE ,  ALTER TABLE , or  CREATE INDEX , as shown in the following examples: CREATE TABLE t1 (id INT); CREATE INDEX id_index ON t1 (id) COMMENT ’MERGE_THRESHOLD=40’; You cannot modify the  MERGE_THRESHOLD  value at the index level for GEN_CLUST_INDEX , which is the clustered index created by  InnoDB  when an InnoDB  table is created without a primary key or unique key index. You can only modify the  MERGE_THRESHOLD  value for  GEN_CLUST_INDEX  by setting MERGE_THRESHOLD  for the table. The current  MERGE_THRESHOLD  value for an index can be obtained by querying the  INNODB_INDEXES table. For example: You can use  SHOW CREATE TABLE  to view the  MERGE_THRESHOLD  value for a table, if explicitly defined using the  table_option COMMENT  clause: 3143 mysql>  SHOW CREATE TABLE t2 \G *************************** 1. row *************************** Table: t2 Create Table: CREATE TABLE ‘t2‘ ( ‘id‘ int(11) DEFAULT NULL, KEY ‘id_index‘ (‘id‘) COMMENT ’MERGE_THRESHOLD=40’ mysql>  SELECT * FROM INFORMATION_SCHEMA.INNODB_INDEXES WHERE NAME=’id_index’ \G *************************** 1. row *************************** INDEX_ID: 91 NAME: id_index TABLE_ID: 68 TYPE: 0 N_FIELDS: 1 PAGE_NO: 4 SPACE: 57 MERGE_THRESHOLD: 40 CREATE TABLE t1 ( id INT, KEY id_index (id) ); ALTER TABLE t1 DROP KEY id_index; ALTER TABLE t1 ADD KEY id_index (id) COMMENT ’MERGE_THRESHOLD=40’; CREATE TABLE t1 ( id INT, KEY id_index (id) COMMENT ’MERGE_THRESHOLD=40’ ); Setting MERGE_THRESHOLD for Individual Indexes Note Querying the MERGE_THRESHOLD Value for an Index •Setting  MERGE_THRESHOLD  for an individual index using  CREATE INDEX : •Setting  MERGE_THRESHOLD  for an individual index using  ALTER TABLE : •Setting  MERGE_THRESHOLD  for an individual index using  CREATE TABLE :