func TestJoinsPreload_Issue7013_RelationEmpty(t *testing.T) {
	type (
		Furniture struct {
			gorm.Model
			OwnerID *uint
		}

		Owner struct {
			gorm.Model
			Furnitures []Furniture
			CompanyID  *uint
			Company    Company
		}

		Building struct {
			gorm.Model
			Name    string
			OwnerID *uint
			Owner   Owner
		}
	)

	DB.Migrator().DropTable(&Building{}, &Owner{}, &Furniture{})

//
//	type User struct {
//	  Toys []Toy `gorm:"polymorphic:Owner;"`
//	}
//	type Pet struct {
//	  Toy Toy `gorm:"polymorphic:Owner;"`
//	}
//	type Toy struct {
//	  OwnerID   int
//	  OwnerType string
//	}
func (schema *Schema) buildPolymorphicRelation(relation *Relationship, field *Field) {
	polymorphic := field.TagSettings["POLYMORPHIC"]

	relation.Polymorphic = &Polymorphic{