[jira] Updated: (LUCENE-584) Decouple Filter from BitSet

["Michael Busch (JIRA)" <ji...@apache.org>]

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

Michael Busch updated LUCENE-584:
---------------------------------

    Attachment: lucene-584-take3-part2.patch
                lucene-584-take3-part1.patch

OK, I created a new patch based on the recent feedback.

This patch introduces two new abstract classes:
{code:java}
/**
 * A DocIdSet contains a set of doc ids. Implementing classes must provide
 * a {@link DocIdSetIterator} to access the set. 
 */
public abstract class DocIdSet {
  public abstract DocIdSetIterator iterator();
}

/**
 * This abstract class defines methods to iterate over a set of
 * non-decreasing doc ids.
 */
public abstract class DocIdSetIterator {
  public abstract int doc();
  
  public abstract boolean next() throws IOException;
    
  public abstract boolean skipTo(int target) throws IOException;
}
{code}

Additional changes:

- Scorer extends DocIdSetIterator now.

- Filter.bits(IndexReader) is not abstract anymore. It is deprecated and 
returns null. Added method Filter.getDocIdSet(IndexReader) which returns
new DocIdBitSet(bits(reader)) for backwards compatibility.

- Added getDocIdSet(IndexReader) implementations to all core readers and
deprecated bits(IndexReader). The Filters (e. g. RangeFilter) are now
using OpenBitSet instead of BitSet.

- Made according changes to the SpanFilter classes.

- Fixed a bug in OpenBitSetIterator. It has an integer curDocId now, which
doc() returns. Before doc() sometimes returned wrong values. I also added
TestOpenBitSet (take from current Solr trunk).

I haven't changed the contrib Filter implementations yet, they still use 
the old (deprecated) API. We should address this with a different issue.

All core & contrib tests pass. This patch should also be fully backwards
compatible.

> 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, 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 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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