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https://issues.apache.org/jira/browse/LUCENE-584?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12558997#action_12558997
]
Eks Dev commented on LUCENE-584:
--------------------------------
Michal, would this work?
1. providing default implementation for basic methods that is using skipping
iterator(always there), so it works by default for *all* implementations,
something along the lines:
/**
* A DocIdSet contains a set of doc ids. Implementing classes must provide
* a [EMAIL PROTECTED] DocIdSetIterator} to access the set.
*/
public abstract class DocIdSet {
public abstract DocIdSetIterator iterator();
public DocIdSet and(DocIdSet){
// default implementation using *iterator*;
}
public DocIdSet or(DocIdSet){
// default implementation using iterator;
}
}
2. And then we *optimize* particular cases, e.g
public class DocIdBitSet extends DocIdSet{
BitSet bits; // Must be there in order for iterator to work....
public DocIdSetIterator iterator(){
//this is easy...
}
public DocIdSet and(DocIdSet dis){
if (dois instanceof DocIdBitSet) {
//not exactly like this, but the idea is there
this.bits.and(((DocIdBitSet) dis));
return this;
}
return super.and(DocIdSet);
}
}
So it works always, and it works fast if need be, one instanceof check does not
hurt there. Did I miss something obvious?
> 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
> Assignee: Michael Busch
> Priority: Minor
> Fix For: 2.4
>
> Attachments: bench-diff.txt, bench-diff.txt,
> ContribQueries20080111.patch, lucene-584-take2.patch,
> lucene-584-take3-part1.patch, lucene-584-take3-part2.patch,
> lucene-584-take4-part1.patch, lucene-584-take4-part2.patch, lucene-584.patch,
> Matcher-20070905-2default.patch, Matcher-20070905-3core.patch,
> Matcher-20071122-1ground.patch, Some Matchers.zip, Test20080111.patch
>
>
> {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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