Scoring, "numDocs" should be number after applying filters, not entire index
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Key: SOLR-1158
URL: https://issues.apache.org/jira/browse/SOLR-1158
Project: Solr
Issue Type: Improvement
Components: search
Affects Versions: 1.4
Reporter: David Smiley
Priority: Minor
I'd like to put different types of things to search for in my Solr index. I
use a "type" field to discriminate between these types of things, and my "id"
primary key field incorporates the type (ex: "FooType:53") to ensure
uniqueness. A problem I see with this approach is that the idf (inverse
document frequency) component of the score is based on the entire index and not
the type that I'm querying. In particular "numDocs" given to the
Similarity.java implementation is the total number of documents in the index.
I think it would be more accurate for numDocs to be the filtered number of
docs. That is the number of docs after the filter queries are applied.
The only issue I see with this which may or may not be a problem is that the
scores (and thus potentially result ordering if sorting by score) would change
depending on which filters are applied. That could be counter-intuitive in a
faceting UI. Perhaps only a certain filter or filters could be marked as
lowering numDocs for scoring. Such a configuration choice strikes me as
belonging in the schema.
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