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From "Paul Elschot (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-1187) Things to be done now that Filter is independent from BitSet
Date Tue, 13 May 2008 22:55:55 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-1187?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12596556#action_12596556
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Paul Elschot commented on LUCENE-1187:
--------------------------------------

That sounds like the overhead of the DocIdSetIterator is never more than directly using an
OpenBitSet in the dense cases that you tested so far (1 in 6 is more than 1 bit per byte).

That means that a DocIdSetIterator should have acceptable performance in the sparse case when
it uses a SortedVIntList underneath. Could you share some test results for sparse cases as
well? I'd expect it to outperform OpenBitSet even at CPU time when it is sparse enough.

> Things to be done now that Filter is independent from BitSet
> ------------------------------------------------------------
>
>                 Key: LUCENE-1187
>                 URL: https://issues.apache.org/jira/browse/LUCENE-1187
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: contrib/*, Search
>            Reporter: Paul Elschot
>            Assignee: Michael Busch
>            Priority: Minor
>         Attachments: BooleanFilter20080325.patch, ChainedFilterAndCachingFilterTest.patch,
Contrib20080325.patch, Contrib20080326.patch, Contrib20080427.patch, javadocsZero2Match.patch,
OpenBitSetDISI-20080322.patch
>
>
> (Aside: where is the documentation on how to mark up text in jira comments?)
> The following things are left over after LUCENE-584 :
> For Lucene 3.0  Filter.bits() will have to be removed.
> There is a CHECKME in IndexSearcher about using ConjunctionScorer to have the boolean
behaviour of a Filter.
> I have not looked into Filter caching yet, but I suppose there will be some room for
improvement there.
> Iirc the current core has moved to use OpenBitSetFilter and that is probably what is
being cached.
> In some cases it might be better to cache a SortedVIntList instead.
> Boolean logic on DocIdSetIterator is already available for Scorers (that inherit from
DocIdSetIterator) in the search package. This is currently implemented by ConjunctionScorer,
DisjunctionSumScorer,
> ReqOptSumScorer and ReqExclScorer.
> Boolean logic on BitSets is available in contrib/misc and contrib/queries
> DisjunctionSumScorer calls score() on its subscorers before the score value actually
needed.
> This could be a reason to introduce a DisjunctionDocIdSetIterator, perhaps as a superclass
of DisjunctionSumScorer.
> To fully implement non scoring queries a TermDocIdSetIterator will be needed, perhaps
as a superclass of TermScorer.
> The javadocs in org.apache.lucene.search using matching vs non-zero score:
> I'll investigate this soon, and provide a patch when necessary.
> An early version of the patches of LUCENE-584 contained a class Matcher,
> that differs from the current DocIdSet in that Matcher has an explain() method.
> It remains to be seen whether such a Matcher could be useful between
> DocIdSet and Scorer.
> The semantics of scorer.skipTo(scorer.doc()) was discussed briefly.
> This was also discussed at another issue recently, so perhaps it is wortwhile to open
a separate issue for this.
> Skipping on a SortedVIntList is done using linear search, this could be improved by adding
multilevel skiplist info much like in the Lucene index for documents containing a term.
> One comment by me of 3 Dec 2008:
> A few complete (test) classes are deprecated, it might be good to add the target release
for removal there.

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