Core Data: Compound Indexes are not getting created on a child entity

Here is the situation: I have a parent - child Core Data model relationship. I have some fields on the child entity which I order by using sort descriptors on a fetch request. I have added them on the Indexes list on the Entity section of the Data Model Inspector like field1,field2.

However, when setting -com.apple.CoreData.SQLDebug 1, I cannot see the compound index being created. Further more, I was able to get the SQLite generated file, and all I can see are the single field indexes created for other purposes, but not the compound ones.

Is there a limitation by doing this on a child entity? Has anyone achieved creating compound indexes on child entities? Thanks!