On 04/05/2011 12:39, Ahmet Arslan wrote:
Im receiving a number of searches with many ORs so that the total number of
matches is huge (> 1 million) although only the first 20 results are required.
Analysis shows most time is spent scoring the results. Now it seems to me if you
sending a query with 10 OR components, documents that match most of the terms are
bound to get a better score than a match that only matches one or two of the
terms. So does lucene do any optimization to not bother working out the scores of
the poor matches.
EDIT:Actually not sure the statement because if only term matches it could
still get the highest score if the match was on the shortest term.
But can you see my point is there way to get lucene discount the less good
matches without scoring them, or is there another approach. At the moment we
allow the full lucene syntax and use QueryParser to parse a query and pass the
resultant query to search unchanged (execpt for handling of numeric fields),
should I be modifying the query somehow ?
You can restrict number of returned results by using a adaptively computed
BooleanQuery.html#setMinimumNumberShouldMatch(int) parameter.
For example, If you have 10 optional clauses you can set minimum should match
to 60% of 10 = 6.
Similar mechanism exists in solr :
http://wiki.apache.org/solr/DisMaxQParserPlugin#mm_.28Minimum_.27Should.27_Match.29
Thanks for the hint, so this could be done by overriding
getBooleanQuery() in QueryParser ?
Paul
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