public TupleIterator<T> iterator() {
        try {
            this.commit();
            return new TupleIteratorImpl(persistentTable.iterator());
        } catch (Exception e) {
            throw new RuntimeException("Failed to open hashtable iterator.", e);
        }
    }
DEPRECATED: may cause OutOfMemoryError on large crawls.

@return
ache/src/main/java/achecrawler/util/persistence/PersistentHashtable.java