I do have a DB on MySQL Galera 5.6.34 with a table that contains an index on ID,date. The table is fully functional and I have used repair and check to verify the table. However, upon backup/restore the importing DB-Server (MySQL 5.7.17, not Galera) tells me there is a duplicate entry and stops importing:
gunzip < DB_170206_040001.sql.gz | mysql -u root -p staging
ERROR 1062 (23000) at line 3800: Duplicate entry '329610-2011-03-27 03:00:00' for key 'user_id'
If I empty that table prior to the backup, everything works fine.
Is there a command to "ignore" upon import, or even better to resolve the problem at the live server?