Cannot ORDER BY when querying Custom Metadata

Question

I have Custom Metadata types with simple relationships between them. When I query them with a relationship query and try to ORDER BY, only 1 of the inner records is returned.

I run this in Anonymous Apex:

Id tmp = ''; // This is populated, I'm just not putting it here
List<Parent__mdt> tmpList = [SELECT Id, MasterLabel, Custom_Order__c, Super__c,
                             (SELECT Id, MasterLabel, Custom_Order__c,
                              FROM Childs__r) 
                             FROM Parent__mdt 
                             WHERE Super__c = :tmp 
                             ORDER BY Custom_Order__c ASC NULLS FIRST];

System.debug(tmpList[0].Childs__r.size());

...and I correctly see that there are 36 'Child' metadata records within that Parent. However, running the same code with an ORDER BY in the relationship clause:

Id tmp = ''; // Again, this is populated
List<Parent__mdt> tmpList = [SELECT Id, MasterLabel, Custom_Order__c, Super__c,
                             (SELECT Id, MasterLabel, Custom_Order__c,
                              FROM Childs__r
                              ORDER BY Custom_Order__c) 
                             FROM Parent__mdt 
                             WHERE Super__c = :tmp 
                             ORDER BY Custom_Order__c ASC NULLS FIRST];

System.debug(tmpList[0].Childs__r.size());

...returns only 1 'Child' within the Parent.

Is this documented anywhere? Is there a way around this?

Answer 1

You can order by with only non relationship fileds for custom mera datatype as per documentation. Check out this link https://resources.docs.salesforce.com/204/latest/en-us/sfdc/pdf/custom_metadata_types_impl_guide.pdf