turn off auto index for foreign key

["Tommy Cheng" <csckcac@xxxxxxxxx>]

Hi admins,
  I would like to turn off the auto index for child table's foreign key. It is because i want to read the information_schema for table, column, index, unique and so on after creating the database. How to turn off the auto behavior? Or Is there a way to distinguish between auto one and user created index?
  Thanks
Tommy Cheng