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".
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?
Then a query can use the pseudo-field "synonym" any place:
"+synonym:big dog"
expands to:
"+(big large^.9 huge^.9) dog"
If so cool, I've wanted an extensible query parser for a while..
thx, Dave
PS
When I wrote up my ideas on this a while ago I though the psuedo-field should look different from the normal fields e.g. it should have 2 colons, not 1, but it's not a huge issue.
Matthew Denner wrote:
Hi,
I have been working with Lucene for about a month now and I am really impressed by the work of the people involved. I did, however, come across something that I thought my be better refactored: extending the QueryParser to add your own handling of various Query implementations. So I had a go at introducing a QueryFactory interface that classes can implement to provide construction of these Query implementations, and then an instance can be passed to a QueryParser instance for it to use. I have a patch that provides this if the developers of Lucene are interested but, because it is a quite dramatic change (it removes alot of deprecated methods which I was very worried about) I would prefer someone to take a look at it and see if they think it is worthwhile.
The reason I made this patch is that I wanted to deal with integer ranges for a particular field in my application and, like I said, extending QueryParser felt wrong to me (and took me almost a week to actually find!). With the patch I write:
QueryParser parser = new QueryParser(
"description", new StandardAnalyzer(),
new SpecialQueryFactory(new QueryFactoryImpl()));
And my specialised QueryFactory implementation gets used during parsing. The implementation of QueryFactoryImpl was created by moving those methods that created Query instances in the original QueryFactory into a separate class. I also created a MultiFieldQueryFactory implementation that takes the methods from MultiFieldQueryParser (effectively making it now redundant).
Personally I prefer the idea of composition over inheritance, in this circumstance, but I can understand why other people would not want this.
Anyway, if someone would like to see the patch (made against the HEAD of the Lucene CVS code) I can provide it; or you can tell me where to go! Either way, Lucene has still made searching so much easier and I thank you.
Matt
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