[LUCENE-5101] make it easier to plugin different bitset implementations to CachingWrapperFilter

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 4.5, 6.0
• Lucene Fields: New
• Assignee: Unassigned
• Reporter: Robert Muir
• Created: 11/Jul/13 02:10
• Updated: 28/Aug/22 13:49
• Resolved: 06/Sep/13 10:19

Description

Currently this is possible, but its not so friendly:

  protected DocIdSet docIdSetToCache(DocIdSet docIdSet, AtomicReader reader) throws IOException {
    if (docIdSet == null) {
      // this is better than returning null, as the nonnull result can be cached
      return EMPTY_DOCIDSET;
    } else if (docIdSet.isCacheable()) {
      return docIdSet;
    } else {
      final DocIdSetIterator it = docIdSet.iterator();
      // null is allowed to be returned by iterator(),
      // in this case we wrap with the sentinel set,
      // which is cacheable.
      if (it == null) {
        return EMPTY_DOCIDSET;
      } else {
/* INTERESTING PART */
        final FixedBitSet bits = new FixedBitSet(reader.maxDoc());
        bits.or(it);
        return bits;
/* END INTERESTING PART */
      }
    }
  }

Is there any value to having all this other logic in the protected API? It seems like something thats not useful for a subclass... Maybe this stuff can become final, and "INTERESTING PART" calls a simpler method, something like:

protected DocIdSet cacheImpl(DocIdSetIterator iterator, AtomicReader reader) {
  final FixedBitSet bits = new FixedBitSet(reader.maxDoc());
  bits.or(iterator);
  return bits;
}