no_empty - Not storing empty keys or attributes

The option indicates, that empty key values are not accepted in the index. A key value is considered as empty, when all its key components contain empty values.

When trying to store instances having empty values for not-empty keys or not-empty attributes, storing the instance in the index is suppressed, but no error is thrown. Thus, the option acts as a sort of filter when maintaining the index.

When the option is set for an owning collection, instances with empty attributes for key component values cannot be created.