relForeignFields = append(relForeignFields, ref.PrimaryKey)
				foreignFields = append(foreignFields, ref.ForeignKey)
			}
		}

		identityMap, foreignValues = schema.GetIdentityFieldValuesMap(tx.Statement.Context, reflectValue, foreignFields)
		if len(foreignValues) == 0 {
			return nil
		}
	}

	// nested preload
	for p, pvs := range preloads {
		tx = tx.Preload(p, pvs...)
	}