Things to be done with now that Filter is indendent from BitSet
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                 Key: LUCENE-1187
                 URL: https://issues.apache.org/jira/browse/LUCENE-1187
             Project: Lucene - Java
          Issue Type: Improvement
            Reporter: Paul Elschot
            Priority: Minor


(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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