protected @NotNull InputDataDiffBuilder<Key, Value> getKeysDiffBuilder(int inputId) throws IOException {
    if (myForwardIndex != null) {
      if (myUseIntForwardIndex) {
        return ((IntForwardIndexAccessor<Key, Value>)myForwardIndexAccessor).getDiffBuilderFromInt(inputId,
                                                                                                   ((IntForwardIndex)myForwardIndex).getInt(
                                                                                                     inputId));
      }
      else {
        return myForwardIndexAccessor.getDiffBuilder(inputId, myForwardIndex.get(inputId));
      }
    }
    return new EmptyInputDataDiffBuilder<>(inputId);
  }
protected @NotNull InputDataDiffBuilder<Key, Value> getKeysDiffBuilder(int inputId)