public synchronized void decrSd(byte[] sdHash) {
    ByteArrayWrapper byteArray = new ByteArrayWrapper(sdHash);
    StorageDescriptorWrapper sdWrapper = sdCache.get(byteArray);
    sdWrapper.refCount--;
    if (sdWrapper.getRefCount() == 0) {
      sdCache.remove(byteArray);
    }
  }
Replaces the old db object with the new one. This will add the new database to cache if it does
not exist.
standalone-metastore/metastore-server/src/main/java/org/apache/hadoop/hive/metastore/cache/SharedCache.java