public @NotNull PersistentEnumeratorStatistics getStatistics() throws IOException {
    lockStorageRead();
    try {
      return new PersistentEnumeratorStatistics(myBTree.getStatistics(),
                                                myCollisions,
                                                myValuesCount,
                                                myKeyStorage.getCurrentLength(),
                                                myCollisionResolutionStorage.length());
    }
    finally {
      unlockStorageRead();
    }
  }
public @NotNull PersistentEnumeratorStatistics getStatistics()