Metadata Relationships Now Support Field Definition Relationships

Metadata relationship fields for custom metadata types now let you look up field definitions. Previously, you could look up entity definitions for standard and custom Salesforce objects, but not a specific field on an object. Now, field definitions are supported as a type of metadata relationship field.
Field Definition option when creating a metadata relationship field Entity definition as the controlling ield for the metadata relationship
The Field Definition option is available whenever the custom metadata type has at least one relationship to Entity Definition.
  • The relationship to Entity Definition is the controlling field.
  • The relationship to Field Definition specifies the standard or custom field from the entity definition object.
On the details page, set the Controlling Field to the relationship to Entity Definition.

When adding a record to the custom metadata type that has the relationship fields, select the specific object and field to reference. For example, select the Industry field on the Account object.When adding a custom metadata type record, specify the object and field that's referenced by the metdata relationship

When creating a view and filter on a field definition relationship field, two separate filters are required—the field definition and the controlling entity definition. Filtering by the field definition relationship field alone isn’t enough. For example, to view all records that look up the Industry field on Account, make sure that the filter criteria specify the API names of the object and field.Filter criteria for a field definition relationship field specify API names of both the field definition and the entity definition

Note these other related changes.
  • In the Metadata API, MetadataRelationshipControllingField is new.
  • In the user interface, the field description for the Metadata Relationship field type has been expanded to include the entity definition and field definition relationship options.