@Override
  public CloseableIterator<IndexStoreEntry> iterator(Collection keysToRemove) {
    return new MemoryIndexStoreIterator(valueToEntriesMap, null, keysToRemove);
  }
Find the old key by traversing the forward map in case of in-place update modification If not
found it means the value object was modified with same value. So oldKey is same as newKey.
geode-core/src/main/java/org/apache/geode/cache/query/internal/index/MemoryIndexStore.java