@Override
  public void put(OrcInputFormat.FooterCacheKey key, OrcTail orcTail) throws IOException {
    localCache.put(key.getPath(), orcTail);
    if (key.getFileId() != null) {
      try {
        externalCacheSrc.getCache(conf).putFileMetadata(Lists.newArrayList(key.getFileId()),
            Lists.newArrayList(orcTail.getSerializedTail()));
      } catch (HiveException e) {
        throw new IOException(e);
      }
    }
  }
Metastore-based footer cache storing serialized footers. Also has a local cache.
ql/src/java/org/apache/hadoop/hive/ql/io/orc/ExternalCache.java