On 26/02/2013 17:22, Uwe Schindler wrote:
Hi,
You cannot override rewrite() because you could easily break the logic
behind TopTermsRewrite. If you want another behavior, subclass another
base class and wrap the TopTermsRewrite instead of subclassing it (the
generics also enforce that the rewrite needs to rewrite() to a class that’s
specified in the generics parameter).
addClause() is not final, its abstract. There is one "final" helper method used
by the rewrite itself, but the methods you need to override are abstract.
Also your generics seem to be wrong, leading to the above question...
In addition, you cast the call to super.rewrite() to DisjMaxQuery, so it is definitely a
DisjMaxQuery (because getTopLevelQuery() always returns one, see generics). You then pass
this DisjMaxQuery to this "getQueryBoostMethod", which checks for instanceof
PrefixQuery. This can never return true, so the boost is always 1. You can therefore nuke
the whole rewrite method (as it changes nothing) and only implement getToplevelQuery()
and addClause().
Uwe
Thanks Uwe, like I said I didn't really understand what I was doing but
it did seem to do the job, I'll try out your recommendations
Paul
-----Original Message-----
From: Paul Taylor [mailto:paul_t...@fastmail.fm]
Sent: Tuesday, February 26, 2013 5:34 PM
To: java-user@lucene.apache.org
Subject: Uable to extends TopTermsRewrite in Lucene 4.1
In Lucene 3.6 I had code that replicated a Dismax Query, and the
search used fuzzy queries in some cases to match values. But I was
finding the score attributed to matches on fuzzy searches was
completely different to the score attributed to matches on exact
searches so the total score returned was not good. I improved this by
extends TopTermsRewrite so that if the query is a prefix query we
boost it as if was exact match, I dont fully understand this but it
improved things somewhat, but in Lucene 4.1 the
rewrite() and addClause() methods are final
So how can I implement this in Lucene 4.1, do I even need to - is
there a more intuitive way to improve the scoring.
This is what I currently have that wont compile because of the final
methods
//TODO FIXME WAS Overriding methods that are now final
public static class MultiTermUseIdfOfSearchTerm<Q extends
DisjunctionMaxQuery> extends TopTermsRewrite<Query> {
//public static final class MultiTermUseIdfOfSearchTerm extends
TopTermsRewrite<BooleanQuery> {
private final TFIDFSimilarity similarity;
public MultiTermUseIdfOfSearchTerm(int size) {
super(size);
this.similarity = new DefaultSimilarity();
}
@Override
protected int getMaxSize() {
return BooleanQuery.getMaxClauseCount();
}
@Override
protected DisjunctionMaxQuery getTopLevelQuery() {
return new DisjunctionMaxQuery(0.1f);
}
@Override
protected void addClause(Query topLevel, Term term, float boost) {
final Query tq = new ConstantScoreQuery(new TermQuery(term));
tq.setBoost(boost);
((DisjunctionMaxQuery)topLevel).add(tq);
}
protected float getQueryBoost(final IndexReader reader, final
MultiTermQuery query)
throws IOException {
float idf = 1f;
float df;
if (query instanceof PrefixQuery)
{
PrefixQuery fq = (PrefixQuery) query;
df = reader.docFreq(fq.getPrefix());
if(df>=1)
{
//Same as idf value for search term, 0.5 acts as length
norm
idf = (float)Math.pow(similarity.idf((int) df,
reader.numDocs()),2) * 0.5f;
}
}
return idf;
}
@Override
public Query rewrite(final IndexReader reader, final
MultiTermQuery
query) throws IOException {
DisjunctionMaxQuery bq =
(DisjunctionMaxQuery)super.rewrite(reader, query);
float idfBoost = getQueryBoost(reader, query);
Iterator<Query> iterator = bq.iterator();
while(iterator.hasNext())
{
Query next = iterator.next();
next.setBoost(next.getBoost() * idfBoost);
}
return bq;
}
}
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