* if the operand type is unknown
*/
private String getSelectorName(DynamicOperand operand)
throws UnsupportedRepositoryOperationException {
if (operand instanceof FullTextSearchScore) {
FullTextSearchScore ftss = (FullTextSearchScore) operand;
return ftss.getSelectorName();
} else if (operand instanceof Length) {
Length length = (Length) operand;
return getSelectorName(length.getPropertyValue());
} else if (operand instanceof LowerCase) {
LowerCase lower = (LowerCase) operand;