private Expression parseConstantOperand(ConstantContext constantContext) {
    String text = constantContext.getText();
    if (constantContext.boolean_literal() != null) {
      return new ConstantOperand(TSDataType.BOOLEAN, text);
    } else if (constantContext.STRING_LITERAL() != null) {
      return new ConstantOperand(TSDataType.TEXT, parseStringLiteral(text));
    } else if (constantContext.INTEGER_LITERAL() != null) {
      return new ConstantOperand(TSDataType.INT64, text);
    } else if (constantContext.realLiteral() != null) {
      return parseRealLiteral(text);
    } else if (constantContext.BINARY_LITERAL() != null) {
      BinaryLiteral binaryLiteral = new BinaryLiteral(text);
      return new ConstantOperand(
          TSDataType.BLOB, BaseEncoding.base16().encode(binaryLiteral.getValues()));
    } else if (constantContext.dateExpression() != null) {
      return new ConstantOperand(
          TSDataType.INT64,
          String.valueOf(
              parseDateExpression(
                  constantContext.dateExpression(),
                  CommonDescriptor.getInstance().getConfig().getTimestampPrecision())));
    } else {
      throw new SemanticException("Unsupported constant operand: " + text);
    }
  }
function for parsing file path used by LOAD statement.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/parser/ASTVisitor.java