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From "Paul Elschot (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-584) Decouple Filter from BitSet
Date Thu, 09 Aug 2007 22:29:43 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-584?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12518858
] 

Paul Elschot commented on LUCENE-584:
-------------------------------------

Mark,

I think we are one the same line, it's just that I don't want to go that far now.
Have another look at the title of this issue, it may be in your title bar, but otherwise 
it's quite a bit of scrolling so I'll repeat it here: "Decouple Filter from BitSet". 
That is the main thing that this patch tries to do.

And that also makes it a starting point for caching of different data structures for Filters.
Caching of Filters is very much needed, but I'd rather see that as another issue.

The DefaultMatcher class tries to do some compression by using a SortedVIntList when that
is smaller than a BitSet, and that is about as far as I'd like to go now.

Proost,
Paul Elschot


> 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, Matcher1-ground-20070730.patch,
Matcher2-default-20070730.patch, Matcher3-core-20070730.patch, Matcher4-contrib-misc-20070730.patch,
Matcher5-contrib-queries-20070730.patch, Matcher6-contrib-xml-20070730.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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