On Jun 16, 2005, at 3:03 PM, Sean O'Connor wrote:
The big stumbling block I have at the moment is understanding
whether Terms can be used to find something like a phrase query,
proximity query, or boolean query. I think the answer is no, two
different concepts.
Terms are the heart of searching. All queries boil down to finding
specific terms. A PhraseQuery finds terms exactly side-by-side
position-wise (or near by some slop factor). BooleanQuery is an
aggregation of other primitive queries, so its sort of special in
that it doesn't deal with terms directly, but all primitive
aggregated queries do. A PrefixQuery is not a "primitive" query - it
rewrites itself to a BooleanQuery OR'd with all the matching terms.
So the terms are the "atoms" of Lucene. Hopefully this is in-line
with the conceptual stumbling block.
But I also tend to think that the wheel has already been invented
to find how many times a phrase (i.e. "Lucene in Action") appears
in a document. Before I go digging through the source code, and
possibly creating some rather embarrassing hack(s), I thought I
would check to see if there is a 'right' way to go about this.
Deep within PhraseQuery the number of occurrences is tracked and used
in scoring. But at the high level of searching, that detail is not
exposed. Using IndexSearcher.explain to see the tf() of a
PhraseQuery may help, but by default it'll be the square root of the
number of occurrences. (at least I hope I'm on track with that
explanation - please correct me if I've misspoken) I'd love to hear
how others have done this sort of thing - find the number of
occurrences of a phrase.
Alternatively, any suggestions on what to google, or where to look
to educate myself would be welcome as well.
You're in the right place. Keep asking - we're all here to learn and
share what we know.
Erik
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