That's true, but it's not clear that I want phrase matches. Consider for
example:
"Lucene Download" as a query. I want something that strongly references
"Lucene" (in the title) and strongly references "Download" but "Download
Lucene" or "Lucene Project Download" are better than some page that
happens to contain the exact phrase.
Other examples are "camera review" or "Gonzales scandal"; there's a
whole class of "subject <modifier>" queries that are not really phrase
based, and my corpus isn't large enough to necessarily contain the
phrase anyway.
I agree that many two or three word queries are really best matched by
phrases, but not all. Is it common to use a phrase query with high slop
to overcome the unequal weighting problem?
Also, my interface does support "\"John Bush\"" (ie the user can quote
the phrase if they like) and I would prefer not to infer automatically
that they meant to do so.
Tim
Jason Pump wrote:
You're not using any type of phrase search. Try ->
( (title:"John Bush"^4.0) OR (body:"John Bush") ) AND (
(title:John^4.0 body:John) AND (title:Bush^4.0 body:Bush) )
or maybe
( (title:"John Bush"~4^4.0) OR (body:"John Bush"~4) ) AND (
(title:John^4.0 body:John) AND (title:Bush^4.0 body:Bush) )
Tim Sturge wrote:
I'm following myself up here to ask if anyone has experience or code
with a BooleanQuery that weights the terms it encounters on a product
basis rather than a sum basis.
This would effectively compute the geometric mean of the term score
(rather than the arithmetic mean) and would give me more "middle
bias". It also has the great advantage that it automatically
implements AND (as something without the term has a score of 0.0
which causes the query to go to 0.0 as well.)
I'm curious though why this doesn't already exist. Is it a bad idea
in general (that I will discover once I implement it and look at the
results?) or does it make searching a lot slower?
Thanks,
Tim
Tim Sturge wrote:
I have an index with two different sources of information, one small
but of high quality (call it "title"), and one large, but of lower
quality (call it "body"). I give boosts to certain documents
related to their popularity (this is very similar to what one would
do indexing the web).
The problem I have is a query like "John Bush". I translate that
into " (title:John^4.0 body:John) AND (title:Bush^4.0 body:Bush) ".
But the results I get are:
1. George Bush
...
4. John Kerry
...
10. John Bush
The reason is (looking at explain) that George Bush is scored:
169 = sum(
1 = <match in body with tiny norm for "John">
)
168 = sum(
160 = <title match for "Bush">
8 = <body match for "Bush">
)
)
and John Kerry is similar but reversed. Poor old "John Bush" only
scores:
72 = sum(
40 = (<title match for "John">+<body match>)
32 = (<title match for "Bush">+ <body match>)
)
because his initial boost was only 1/4 of George's.
The question I have is, how can tell the searcher to care about
"balance"? I really want the score over 2 terms to be more like
(sqrt(X)+sqrt(Y))^2 or maybe even exp(log(X)+log(Y)) rather than
just X+Y. Is that supported in some obvious way, or is there some
other way to phrase my query to say "I want both terms but they
should both be important if possible?"
Thanks,
Tim
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