Wenhai created LUCENE-8123:
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Summary: Question about how to retrieve by TFIDFSimilarity query
on lucene
Key: LUCENE-8123
URL: https://issues.apache.org/jira/browse/LUCENE-8123
Project: Lucene - Core
Issue Type: Bug
Components: core/query/scoring
Affects Versions: 7.2
Reporter: Wenhai
Priority: Minor
Hi, all.
Recently, we were performing experiment on Lucene based on TFIDF.
We want to get the similar documents from the corpus, of which the
similarity each document (d) and the given query (q) is no less than a
threshold. We use the following scoring function.
sum(tf(t,d) * idf(t) * tf(t,q) * idf(t))/(norm(d) * norm(q))
where norm is defined as sqrt( sum(tf(t,d) * idf(t) * tf(t,d) * idf(t)) ).
We perform this query by scanning the related docIds of all terms in the
query, and the related docIds are derived from function PostingsEnum docEnum =
MultiFields.getTermDocsEnum(indexReader, "text", terms.get(i).bytes()) . After
the inner products of these related documents have been computed, the final
similarities are computed by dividing these inner products by their norm.
However, when the documents scale up, e.g., more than ten million document,
the runtime is unacceptable (more than ten seconds). Does Lucene provide more
efficient interface to generate ranked results based on TFIDF?
Best
Wenhai
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