lucene-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Paul Elschot (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-584) Decouple Filter from BitSet
Date Tue, 10 Apr 2007 07:23:32 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-584?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12487706
] 

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

That could be improved in a DisjunctionMatcher.
With a bit of bookkeeping DisjunctionSumScorer could also delay calling score() on the subscorers
but the bookkeeping would affect performance for the normal case.

For the usual queries the score() call will never have much of a performance impact.
The reason for this is that TermScorer.score() is really very efficient, iirc it caches
weighted tf() values for low term frequencies.
All the rest is mostly additions, and occasionally a multiplication for a coordination factor.

To determine which documents match the query, the index need to be accessed,
and that takes more time than score value computations because the complete index
almost never fits in the fastest cache.



> 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, BitsMatcher.java, Filter-20060628.patch,
HitCollector-20060628.patch, IndexSearcher-20060628.patch, MatchCollector.java, Matcher.java,
Matcher20070226.patch, Scorer-20060628.patch, Searchable-20060628.patch, Searcher-20060628.patch,
Some Matchers.zip, SortedVIntList.java, TestSortedVIntList.java
>
>
> {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=.

-- 
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.


---------------------------------------------------------------------
To unsubscribe, e-mail: java-dev-unsubscribe@lucene.apache.org
For additional commands, e-mail: java-dev-help@lucene.apache.org


Mime
View raw message