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From "Michael Busch (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-1187) Things to be done now that Filter is independent from BitSet
Date Fri, 14 Mar 2008 07:05:24 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-1187?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12578626#action_12578626
] 

Michael Busch commented on LUCENE-1187:
---------------------------------------

{quote}
Test that now fails with ChainedFilter.
{quote}

The reason apparently is that the core moved from BitSets to OpenBitSets,
whereas the contrib packages haven't.

If we change the contrib packages to also use OpenBitSets, then this is 
still not completely backwards compatible. For example, if a user upgrades
to 2.4, uses a ChainedFilter to combine a 2.4 core filter with their own 
custom Filter that is based on 2.3 and thus uses a BitSet, then it won't
work. So a simple drop-in replacement with the new lucene jar would not
be possible, the user would have to change their own filters.

Maybe we should introduce a DocIdSetFactory in the core? For 
backwards compatibility a factory that produces BitSets can be used,
for speed one that creates OpenBitSets. Thoughts?

> 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
>            Reporter: Paul Elschot
>            Priority: Minor
>         Attachments: ChainedFilterAndCachingFilterTest.patch, javadocsZero2Match.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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