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https://issues.apache.org/jira/browse/LUCENE-5983?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Adrien Grand updated LUCENE-5983:
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Attachment: LUCENE-5983.patch
Here are a patch and the results of the benchmark on this new DocIdSet:
http://people.apache.org/~jpountz/doc_id_sets4.html
Compared to the paper, I also optimized the super-dense case in order to encode
the negation of the set to save space (like WAH8DocIdSet does). I like the fact
that this set is overall very fast, especially to build, which is an
interesting characteristic for caching, so I replaced WAH8DocIdSet with this
new DocIdSet in CachingWrapperFilter. Another nice property is that it is
naturally indexed, it doesn't need a side-car data-structure like the WAH8 and
PFOR doc id sets: in the array case, you can just perform a binary search, and
in the FixedBitSet case you already have random-access.
In order to avoid the profusion of doc id sets, I'm thinking of removing the
WAH8 and PFOR doc id sets since this one looks better to me in most areas.
> RoaringDocIdSet
> ---------------
>
> Key: LUCENE-5983
> URL: https://issues.apache.org/jira/browse/LUCENE-5983
> Project: Lucene - Core
> Issue Type: Improvement
> Reporter: Adrien Grand
> Assignee: Adrien Grand
> Priority: Minor
> Attachments: LUCENE-5983.patch
>
>
> Robert pointed me to this paper: http://arxiv.org/pdf/1402.6407v4 that
> describes an interesting way to build doc id sets: The bit space is divided
> into blocks of 2^16 bits so that you can store the bits which are set either
> in a short[] (2 bytes per doc ID) or in a FixedBitSet. The choice is easy, if
> less than 2^12 bits are set, then the short[] representation is more compact
> otherwise a FixedBitSet would be more compact. It's quite similar to the way
> that Solr builds DocSets in {{SolrIndexSearcher.getDocSet(DocsEnumState)}}.
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