private boolean processBbResult(
      ByteBuffer bb, int ix, HdfsFileStatusWithId file, OrcTail[] result) throws IOException {
    if (bb == null) {
      return true;
    }
    result[ix] = createOrcTailFromMs(file, bb);
    if (result[ix] == null) {
      return false;
    }

    localCache.put(file.getFileStatus().getPath(), result[ix]);
    return true;
  }
Metastore-based footer cache storing serialized footers. Also has a local cache.
ql/src/java/org/apache/hadoop/hive/ql/io/orc/ExternalCache.java