docs: private void registerOperandSubQueries(
  		SqlValidatorScope parentScope,
  		SqlCall call,
  		int operandOrdinal) {
  		SqlNode operand = call.operand(operandOrdinal);
  		if (operand == null) {
  			return;
  		}
  		if (operand.getKind().belongsTo(SqlKind.QUERY)
  			&& call.getOperator().argumentMustBeScalar(operandOrdinal)) {
  			operand =
  				SqlStdOperatorTable.SCALAR_QUERY.createCall(
  					operand.getParserPosition(),
  					operand);
  			call.setOperand(operandOrdinal, operand);
  		}
  		registerSubQueries(parentScope, operand);
  	}