Upon proceedings for the foreclosure of any judgment lien, when the judgment creditor holds a mortgage upon real estate in this state as security for the debt, or any part of it, that has gone into the judgment, which mortgage is a first charge upon the property mortgaged, the court shall, upon the motion of the judgment debtor or any later encumbrancer on the property covered by the judgment lien, order such mortgaged property to be first applied to the debt secured by it, at its cash value, to be ascertained by the court; and a foreclosure of the judgment lien shall be granted only as to the portion of such judgment that remains unsatisfied.