private Long generateTestFileId(final FileStatus fs, List<HdfsFileStatusWithId> files, int i) {
    final Long fileId = HdfsUtils.createTestFileId(fs.getPath().toUri().getPath(), fs, false, null);
    files.set(i, new HdfsFileStatusWithId() {
      @Override
      public FileStatus getFileStatus() {
        return fs;
      }

      @Override
      public Long getFileId() {
        return fileId;
      }
    });
    return fileId;
  }
Metastore-based footer cache storing serialized footers. Also has a local cache.
ql/src/java/org/apache/hadoop/hive/ql/io/orc/ExternalCache.java