shillelagh-processor/src/main/java/shillelagh/internal/ShillelaghProcessor.java
private void checkForTableId(TableObject tableObject, Element element) {
    // Check if user wants to use an id other than _id
    Id idAnnotation = element.getAnnotation(Id.class);
    if (idAnnotation != null) {
      if (element.asType().getKind() != TypeKind.LONG && !("java.lang.Long".equals(
          element.asType().toString()))) {
        logger.e("@Id must be on a long");
      }

      // Id attribute set and continue
      String columnName = Strings.isBlank(idAnnotation.name()) //
          ? element.getSimpleName().toString() //
          : idAnnotation.name();

      final TableColumn idColumn = new TableColumn(columnName, element.getSimpleName().toString(),
          element.asType().toString(), SqliteType.INTEGER);

      tableObject.setIdColumn(idColumn);
    }
  }
private void checkForTableId(TableObject tableObject, Element element) {
    // Check if user wants to use an id other than _id
    Id idAnnotation = element.getAnnotation(Id.class);
    if (idAnnotation != null) {
      if (element.asType().getKind() != TypeKind.LONG && !("java.lang.Long".equals(
          element.asType().toString()))) {
        logger.e("@Id must be on a long");
      }

      // Id attribute set and continue
      String columnName = Strings.isBlank(idAnnotation.name()) //
          ? element.getSimpleName().toString() //
          : idAnnotation.name();

      final TableColumn idColumn = new TableColumn(columnName, element.getSimpleName().toString(),
          element.asType().toString(), SqliteType.INTEGER);

      tableObject.setIdColumn(idColumn);
    }
  }
Check if the element has the @Id annotation if it does use that for it's id