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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