Dear Lucas! I've faced such issue with the loader api: I have a class that contains only id values. This class is actually a composite primary key itself. I want to make batch insert for this class using loader api. But if I use onDuplicateKeyUpdate - I receive an error like there is no fields to update(truth, there is only part of primary key). If I use onDuplicateKeyIgnore - I receive an error Cannot apply batch loading with onDuplicateKeyIgnore flag. If I use nothing - sometimes I face duplicate key violation exception. Can you advice me any approach to deal with this case? I will really appreciate any help.