On Monday 07 February 2005 19:17, David Spencer wrote:
> This is interesting and may match what I've wanted - a way to register
> customized query expansion modules w/ the query parser so that you can
> experiment with different ways of expanding the query e.g. I wrote a
> "WordNet" package that's in the sandbox that expands terms by adding
> their synonyms e.g. "big" might expand to "big large^.9 huge^.9".
I took a quick look at the WordNet CVS and I'm not quite sure so I'm kind of
working off what's below!
> So is it safe to assume I could use your code like this (with 2 lines
> changed from your example):
>
> QueryParser parser =
> new QueryParser(
> "synonym", // pseudo field?
> new StandardAnalyzer(),
> new SpecialQueryFactory(new WordNetQueryFactoryImpl())); //
> wordnet factory?
It would probably be something like:
QueryParser parser =
new QueryParser(
"defaultSearchField", // default search field (as
normal)
new StandardAnalyzer(),
new WordNetQueryFactoryImpl("synonym", new QueryFactoryImpl()));
I'm thinking that an instance of your QueryFactory implementation would
effectively decorate another instance and might have your pseudo-field passed
as a parameter. It would then be implemented to catch any pseudo-field (in
this case "synonym") queries and process the text itself.
> Then a query can use the pseudo-field "synonym" any place:
>
> "+synonym:big dog"
>
> expands to:
>
> "+(big large^.9 huge^.9) dog"
Your WordNetQueryFactoryImpl would be something like this:
public class WordNetQueryFactoryImpl implements QueryFactory {
private final QueryFactory m_delegate;
private final String m_pseudoField;
public WordNetQueryFactoryImpl(String pseudoField, QueryFactory delegate) {
m_pseudoField = pseudoField;
m_delegate = delegate;
}
// ... a few other interface methods here but cut for clarity ...
public Query getFieldQuery(
String field,
Analyzer analyzer,
String queryText,
int slop)
{
// If the field is our pseudo-field and the value for it is 'big'
if (m_pseudoField.equals(field) && "big".equals(queryText)) {
// Use the delegate to build our query?
BooleanQuery tmp = new BooleanQuery();
tmp.add(
m_delegate.getFieldQuery(field, analyzer, "big", slop),
BooleanClause.Occur.SHOULD);
tmp.add(
m_delegate.getFieldQuery(field, analyzer, "large", slop),
BooleanClause.Occur.SHOULD);
tmp.add(
m_delegate.getFieldQuery(field, analyzer, "huge", slop),
BooleanClause.Occur.SHOULD);
return tmp;
} else {
// ... otherwise delegate the handling to the other QueryFactory
return m_delegate.getFieldQuery(field, analyzer, queryText, slop);
}
}
}
Just as an example, I'm sure you'll work out what I mean!
> If so cool, I've wanted an extensible query parser for a while..
I don't think it quite fits an "extensible query parser", but I think it might
get you somewhere.
Matt
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