@Override
  public void commit(WriterContext context) throws HCatException {
    WriterContextImpl cntxtImpl = (WriterContextImpl)context;
    try {
      new HCatOutputFormat().getOutputCommitter(
          ShimLoader.getHadoopShims().getHCatShim().createTaskAttemptContext(
              cntxtImpl.getConf(),
              ShimLoader.getHadoopShims().getHCatShim().createTaskAttemptID()))
          .commitJob(ShimLoader.getHadoopShims().getHCatShim().createJobContext(
              cntxtImpl.getConf(), null));
    } catch (IOException e) {
      throw new HCatException(ErrorType.ERROR_NOT_INITIALIZED, e);
    } catch (InterruptedException e) {
      throw new HCatException(ErrorType.ERROR_NOT_INITIALIZED, e);
    }
  }
This writer writes via {@link HCatOutputFormat}
hcatalog/core/src/main/java/org/apache/hive/hcatalog/data/transfer/impl/HCatOutputFormatWriter.java