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From "Paul Elschot (JIRA)" <>
Subject [jira] Commented: (LUCENE-584) Decouple Filter from BitSet
Date Thu, 30 Aug 2007 19:12:31 GMT


Paul Elschot commented on LUCENE-584:

This set of patches indeed break backward compatibility with the current Filter class.
That was done to show the ideal end situation, and to make sure that the patched code is indeed

To get backward compatibility I'd prefer to temporarily copy the functionality from BitSetFilter
into the Filter class, while still leaving BitSetFilter as it is:

public class Filter {
   /** @deprecated use class BitSetFilter instead */
  public abstract BitSet bits(IndexReader reader);

  /** this method will become abstract once the bits() method is removed from Filter: */
  public Matcher getMatcher(IndexReader reader) {return DefaultFilter.defaultFilter(bits(reader));}

The main difference between the current set of patches and the removed patches is indicated
in my first comment of 25 July 2007 above.
I still have the older versions of the patch lying around here, so if you need a particular
one, just indicated the date, and I'll repost or send 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
>            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
> {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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