select 
        a.index_name as index_name,
        ceil(
        (select count(*) from `test`.`table0`) *(
        @@global.myisam_data_pointer_size + 
        sum(ifnull(1 + `a`.`sub_part` * (`b`.`character_octet_length`/`b`.`character_maximum_length`),
                ifnull(1 + `b`.`character_octet_length`,
                        case 
                                when `b`.`data_type` = 'tinyint' then 1
                                when `b`.`data_type` = 'smallint' then 2
                                when `b`.`data_type` = 'mediumint' then 3
                                when `b`.`data_type` = 'int' then 4
                                when `b`.`data_type` = 'bigint' then 8
                                when `b`.`data_type` = 'float' then 4
                                when `b`.`data_type` = 'double' then 8
                                when `b`.`data_type` = 'real' then 8
                                when `b`.`data_type` = 'bit' then 8
                                when `b`.`data_type` = 'date' then 3
                                when `b`.`data_type` = 'datetime' then 8
                                when `b`.`data_type` = 'timestamp' then 4
                                when `b`.`data_type` = 'time' then 3
                                when `b`.`data_type` = 'year' then 1
                                when `b`.`data_type` = 'enum' then 2
                                when `b`.`data_type` = 'set' then 8
                                when `b`.`data_type` = 'decimal' then 8
                                
                        end
                        )
                      
        )
        + if(`a`.`nullable`='YES',1,0)
        + if(`b`.`character_octet_length` >=255,2,0)
        ))/1048576)*1048576  as `index_size`
from
`information_schema`.`statistics` `a`,
`information_schema`.`columns` `b`
where
        `a`.`table_name`=`b`.`table_name` and
        `a`.`table_schema`=`b`.`table_schema` and
        `a`.`column_name`=`b`.`column_name` and
        `a`.`table_schema`='test' and
        `a`.`table_name`='table0'
                
group by `a`.`index_name`
order by `index_size` desc limit 1;

select * from information_schema.statistics where table_name='table0' and table_schema='test';