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https://issues.apache.org/jira/browse/LUCENE-5101?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13708830#comment-13708830
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Paul Elschot commented on LUCENE-5101:
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I had another look at the recent benchmark results and something does not seem
in order there.
At density -2 (1%), Elias-Fano is faster at advance(docID() +1) (2.45 times
fixed) than at nextDoc() (1.81 times fixed), and I'd the FixedBitSet should
have an almost equal run times for advance(docId()+1) and nextDoc().
The code for advance (advanceToValue in EliasFanoDecoder) is really more
complex than the code for nextDoc (nextValue in EliasFanoDecoder) and the code
at EliasFanoDocIdSet is so simple that it should not really influence things
here.
So for EliasFanoDocIdSet advance(docId() + 1) should normally be slower than
nextDoc(), but the benchmark contradicts this.
Could there be a mistake in the benchmark for these cases? Or is this within
expected (JIT) tolerances?
> make it easier to plugin different bitset implementations to
> CachingWrapperFilter
> ---------------------------------------------------------------------------------
>
> Key: LUCENE-5101
> URL: https://issues.apache.org/jira/browse/LUCENE-5101
> Project: Lucene - Core
> Issue Type: Improvement
> Reporter: Robert Muir
> Attachments: LUCENE-5101.patch
>
>
> Currently this is possible, but its not so friendly:
> {code}
> 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 */
> }
> }
> }
> {code}
> 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:
> {code}
> protected DocIdSet cacheImpl(DocIdSetIterator iterator, AtomicReader reader) {
> final FixedBitSet bits = new FixedBitSet(reader.maxDoc());
> bits.or(iterator);
> return bits;
> }
> {code}
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