Allow creation of foreign keys without automatic index creation for the child table. Or, allow dropping the automatically-created index for the child table. Either way, foreign keys will continue to work despite index absence.
From Peter's "WL#148 Note#1" https://intranet.mysql.com/secure/mailarchive/mail.php?folder=4&mail=19697 " Change#8: ... 4. If pk_column list is omitted, then pk table must have a PRIMARY KEY, just copy the column names from there. Try to support foreign key constraints if there is no key defined on the used tables. " From minutes of a Heidelberg discussions about foreign keys https://inside.mysql.com/wiki/HD_Mtg:_Foreign_Keys_Workshop " Change#8: Agreed Some participants said: We need *separate* WL entry for "support foreign keys when there is no index on the child table." Action item PeterG: Create that WL entry. "