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From "Adrien Grand (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (LUCENE-5101) make it easier to plugin different bitset implementations to CachingWrapperFilter
Date Fri, 12 Jul 2013 19:11:48 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-5101?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13707268#comment-13707268
] 

Adrien Grand commented on LUCENE-5101:
--------------------------------------

A quick note about alternative DocIdSet we now have. I wrote a benchmark (attached) to see
how they compared to FixedBitSet, you can look at the results here: http://people.apache.org/~jpountz/doc_id_sets.html
Please note that EliasFanoDocIdSet is disadvantaged for advance() since it doesn't have an
index yet, it will be interesting to run this benchmark again when it gets one.

Maybe we could use these numbers to have better defaults in CWF? (and only use FixedBitSet
for dense sets for example)
                
> 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
>
> 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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