schema.err = fmt.Errorf("invalid polymorphic foreign keys %+v for %v on field %s", relation.foreignKeys,
					schema, field.Name)
			}
		}

		if primaryKeyField == nil {
			schema.err = fmt.Errorf("invalid polymorphic type %v for %v on field %s, missing primaryKey field",
				relation.FieldSchema, schema, field.Name)
			return
		}

		// use same data type for foreign keys
		if copyableDataType(primaryKeyField.DataType) {