private ParquetMetadata readSplitFooter(JobConf configuration, final Path file,
      Object cacheKey, MetadataFilter filter, CacheTag tag) throws IOException {
    if (cacheKey == null || metadataCache == null) {
      // Non-LLAP case
      FileSystem fs = file.getFileSystem(configuration);
      FileStatus stat = fs.getFileStatus(file);
      return readFooterFromFile(file, fs, stat, filter);
    } else {
      MemoryBufferOrBuffers footerData = LlapProxy.getIo().getParquetFooterBuffersFromCache(file, configuration, cacheKey);
      return ParquetFileReader.readFooter(new ParquetFooterInputFromCache(footerData), filter);
    }
  }
The total number of rows this RecordReader will eventually read. The sum of the
rows of all the row groups.
ql/src/java/org/apache/hadoop/hive/ql/io/parquet/vector/VectorizedParquetRecordReader.java