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https://issues.apache.org/jira/browse/LUCENE-3440?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13120049#comment-13120049
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sebastian L. commented on LUCENE-3440:
--------------------------------------
Another patch for 4.0. This one makes FieldFragList "plugable".
This patch contains:
- Introduction of interface FieldFragList
- Introduction of abstract class BaseFieldFragList which contains SubInfo and
FieldFragInfo (I renamed WeightedFragInfo)
- Introduction of class SimpleFieldFragList (default)
- Introduction of class WeightedFieldFragList
- Introduction of abstract class BaseFragListBuilder
- Introduction of class SimpleFragListBuilder (default)
- Introduction of class WeightedFragListBuilder
The weighting-formula now depends on the implementation of
FieldFragList.add(int startOffset, int endOffset, List<FieldPhraseInfo>
phraseInfoList):
{code:java}
/* (non-Javadoc)
* @see org.apache.lucene.search.vectorhighlight.FieldFragList#getFragInfos()
*/
@Override
public void add( int startOffset, int endOffset, List<FieldPhraseInfo>
phraseInfoList ) {
float score = 0;
List<SubInfo> subInfos = new ArrayList<SubInfo>();
for( FieldPhraseInfo phraseInfo : phraseInfoList ){
subInfos.add( new SubInfo( phraseInfo.getText(),
phraseInfo.getTermsOffset(), phraseInfo.getSeqnum() ) );
score += phraseInfo.getBoost();
}
getFragInfos().add( new FieldFragInfo( startOffset, endOffset, subInfos,
score ) );
}
{code}
The choosen FieldFragList depends on FragListBuilder.createFieldFragList(
FieldPhraseList fieldPhraseList, int fragCharSize ):
{code:java}
/* (non-Javadoc)
* @see
org.apache.lucene.search.vectorhighlight.FragListBuilder#createFieldFragList(FieldPhraseList
fieldPhraseList, int fragCharSize)
*/
@Override
public FieldFragList createFieldFragList( FieldPhraseList fieldPhraseList,
int fragCharSize ){
return createFieldFragList( fieldPhraseList, new SimpleFieldFragList(
fragCharSize ), fragCharSize );
}
{code}
Of course, Solr-config could look like this:
{code:xml}
<highlighter>
<fragListBuilder name="simple"
class="org.apache.solr.highlight.SimpleFragListBuilder"/>
<fragListBuilder name="weighted"
class="org.apache.solr.highlight.WeightedFragListBuilder" default="true"/>
<fragmentsBuilder name="ordered"
class="org.apache.solr.highlight.ScoreOrderFragmentsBuilder" default="true"/>
</highlighter>
{code}
I think, this is the best possible approach, because it maintains
backwards-compatibility, but do also some refactoring which
would/could/should/can make it easier to plug-in different approaches in
future.
But, after a few weeks of banging my head against the wall I have to admit: I
have no idea. ;)
> FastVectorHighlighter: IDF-weighted terms for ordered fragments
> ----------------------------------------------------------------
>
> Key: LUCENE-3440
> URL: https://issues.apache.org/jira/browse/LUCENE-3440
> Project: Lucene - Java
> Issue Type: Improvement
> Components: modules/highlighter
> Affects Versions: 3.5, 4.0
> Reporter: sebastian L.
> Priority: Minor
> Labels: FastVectorHighlighter
> Fix For: 3.5, 4.0
>
> Attachments: LUCENE-3.5-SNAPSHOT-3440-6-ProofOfConcept.java,
> LUCENE-3.5-SNAPSHOT-3440-6.patch, LUCENE-4.0-SNAPSHOT-3440-6.patch,
> WeightOrderFragmentsBuilder_table01.html,
> WeightOrderFragmentsBuilder_table02.html
>
>
> The FastVectorHighlighter uses for every term found in a fragment an equal
> weight, which causes a higher ranking for fragments with a high number of
> words or, in the worst case, a high number of very common words than
> fragments that contains *all* of the terms used in the original query.
> This patch provides ordered fragments with IDF-weighted terms:
> total weight = total weight + IDF for unique term per fragment * boost of
> query;
> The ranking-formula should be the same, or at least similar, to that one used
> in org.apache.lucene.search.highlight.QueryTermScorer.
> The patch is simple, but it works for us.
> Some ideas:
> - A better approach would be moving the whole fragments-scoring into a
> separate class.
> - Switch scoring via parameter
> - Exact phrases should be given a even better score, regardless if a
> phrase-query was executed or not
> - edismax/dismax-parameters pf, ps and pf^boost should be observed and
> corresponding fragments should be ranked higher
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