protected void checkPartitionsMatch(Path inputPath) throws IOException {
    if (!dpPath.equals(inputPath)) {
      // Temp partition input path does not match exist temp path
      String msg = "Multiple partitions for one merge mapper: " + dpPath +
          " NOT EQUAL TO "
          + inputPath;
      LOG.error(msg);
      throw new IOException(msg);
    }
  }
Validates that each input path belongs to the same partition since each
mapper merges the input to a single output directory

@param inputPath - input path
ql/src/java/org/apache/hadoop/hive/ql/exec/AbstractFileMergeOperator.java