>> Could someone give me a hint about conducting a boolean search by
>> using the Lucene/Nutch API's directly? Just some starting points to
>> look at.
> Nutch does not support boolean queries as lucene does. Only the minus
> operator (-) is supported to exclude words from the search. If you
> want boolean query support, then you should modify the Query.java. In
> this class there are subclasses called Clause, Term and Phrase. A
> clause is either a term or a phrase. This class is constructed by the
> Query.parse() method. Parse method delegates to the
> NutchAnalysis.parseQuery(). NutchAnaylsis is generated from
> NutchAnalysis.jj. This JavaCC document lexical analysis and parsing.
> And finally, QueryFilters.filter method run all query filters through
> the Query and these filters convert the nutch Query to lucene
> BooleanQuery. You should definitely check query-basic for this.
>
> To add boolean query support (esp. OR ) you need to modify all the
> above classes in some way : )
>
> Alternatively, you can just construct the Boolean Query and the pass
> it to the index servers bypassing nutch Query class.
I did something different. The "OR" searches I needed where all related
to a custom indexed field I had created with a plugin. This field is
called zip3. What I did is to modify my custom zip3 QueryFilter. I
include the code here (perhaps somebody could find the idea useful).
This query filter transforms a term like: zip3:AAA-BBB-CCC to a search
that could have been written as zip3:AAA OR zip3:BBB OR zip3:CCC.
Here's my code:
public class Zip3QueryFilter extends RawFieldQueryFilter
{
private Configuration conf;
float myBoost = 0f;
public Zip3QueryFilter()
{
super("zip3");
}
public void setConf(Configuration conf)
{
this.conf = conf;
setBoost(conf.getFloat("query.zip3.boost", 0.0f));
}
public Configuration getConf()
{
return this.conf;
}
@Override
public BooleanQuery filter(Query input, BooleanQuery output)
throws QueryException
{
for(Clause c : input.getClauses())
{
if(!c.getField().equals("zip3"))
continue;
String value = c.getTerm().toString();
BooleanQuery bq = new BooleanQuery();
for(String z3 : value.split("-"))
{
TermQuery clause = new TermQuery(new Term(
"zip3", z3));
bq.add(clause, Occur.SHOULD);
}
bq.setBoost(myBoost);
output
.add(
bq,
(c.isProhibited() ? BooleanClause.Occur.MUST_NOT
: (c.isRequired() ? BooleanClause.Occur.MUST
: BooleanClause.Occur.SHOULD)));
}
return output;
}
@Override
protected void setBoost(float boost)
{
super.setBoost(boost);
myBoost = boost;
}
}
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