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https://issues.apache.org/jira/browse/LUCENE-584?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12546166
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Paul Elschot commented on LUCENE-584:
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The patch is backwards compatible, except for current subclasses of Filter
already have a getMatcher method. The fact that no changes are needed to
contrib confirms the compatibility.
I have made no performance tests on BitSetMatcher for two reasons.
The first reason is that OpenBitSet is actually faster than BitSet (have a look
at the graph in the SomeMatchers.zip file attachment by Eks Dev), so it seems
to be better to go in that direction.
The second is that it is easy to do the skipping in IndexSearcher on a BitSet
directly by using nextSetBit on the BitSet instead of skipTo on the
BitSetMatcher. For this it would only be necessary to check whether the given
MatchFilter is a Filter.
Anyway, I prefer to see where the real performance bottlenecks are before
optimizing for performance.
DefaultMatcher should be in the ...2default... patch.
The change in Hits to use MatchFilter should be in the ...3core.. patch.
So far, I never tried to use these patches on their own, I have only split them
for a better overview. Splitting the combined patches to iterate would need a
different split, as you found out. It might even be necessary to split within a
single class, but I'll gladly do that.
> Decouple Filter from BitSet
> ---------------------------
>
> Key: LUCENE-584
> URL: https://issues.apache.org/jira/browse/LUCENE-584
> Project: Lucene - Java
> Issue Type: Improvement
> Components: Search
> Affects Versions: 2.0.1
> Reporter: Peter Schäfer
> Priority: Minor
> Attachments: bench-diff.txt, bench-diff.txt,
> Matcher-20070905-2default.patch, Matcher-20070905-3core.patch,
> Matcher-20071122-1ground.patch, Some Matchers.zip
>
>
> {code}
> package org.apache.lucene.search;
> public abstract class Filter implements java.io.Serializable
> {
> 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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