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From "Michael Busch (JIRA)" <>
Subject [jira] Commented: (LUCENE-584) Decouple Filter from BitSet
Date Thu, 10 Jan 2008 19:19:34 GMT


Michael Busch commented on LUCENE-584:

On the take3 patch of 10 Jan 2008:

Thanks for the review!

PrefixGenerator is used but not defined in the patch, so it will not compile.

Not sure I understand what you mean. PrefixGenerator is (and was) 
defined in It compiles for me.

There is neither a BitSetFilter nor an OpenBitSetFilter in the patch.
These might be useful for existing code currently implementing Filter
to overcome the deprecation of Filter.bits().
With the current core moving to OpenBitSet, it might also use an
explicit OpenBitSetFilter.

I think that it should be straightforward for users having filters that use
BitSets to wrap the new DocIdBitSet around the BitSet, just as Filter currently 
does for backwards compatibility?

Some javadoc changes did not make it into the take3 patch, I'll check these later.

Oh, which ones?

FilteredQuery.explain(): When a document does not pass the Filter
I think it would be better not to use setValue(0.0f) on the resulting
Explanation. However, this may be necessary for backward compatibility.

Yeah, it used to work this way, that's why I didn't change it for backwards-
compatibility reasons.

About adding a Filter as a clause to BooleanScorer, and adding
DocSetIdIterator as a "Scorer" to ConjunctionScorer:
This is the reason for the CHECKME in IndexSearcher for using
ConjunctionScorer when a filter is given.
A ConjunctionScorer that accepts a DocIdSetIterator could also be used in

Well, let's address this with a different issue after this one is committed.
I might have some concerns here, but I've to further think about it.

> Decouple Filter from BitSet
> ---------------------------
>                 Key: LUCENE-584
>                 URL:
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: Search
>    Affects Versions: 2.0.1
>            Reporter: Peter Schäfer
>            Assignee: Michael Busch
>            Priority: Minor
>             Fix For: 2.4
>         Attachments: bench-diff.txt, bench-diff.txt, lucene-584-take2.patch, lucene-584-take3-part1.patch,
lucene-584-take3-part2.patch, lucene-584.patch, Matcher-20070905-2default.patch, Matcher-20070905-3core.patch,
Matcher-20071122-1ground.patch, Some
> {code}
> package;
> public abstract class Filter implements 
> {
>   public abstract AbstractBitSet bits(IndexReader reader) throws IOException;
> }
> public interface AbstractBitSet 
> {
>   public boolean get(int index);
> }
> {code}
> It would be useful if the method =Filter.bits()= returned an abstract interface, instead
of =java.util.BitSet=.
> Use case: there is a very large index, and, depending on the user's privileges, only
a small portion of the index is actually visible.
> Sparsely populated =java.util.BitSet=s are not efficient and waste lots of memory. It
would be desirable to have an alternative BitSet implementation with smaller memory footprint.
> Though it _is_ possibly to derive classes from =java.util.BitSet=, it was obviously not
designed for that purpose.
> That's why I propose to use an interface instead. The default implementation could still
delegate to =java.util.BitSet=.

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