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From "Robert Muir (JIRA)" <j...@apache.org>
Subject [jira] [Resolved] (LUCENE-8123) Question about how to retrieve by TFIDFSimilarity query on lucene
Date Sun, 07 Jan 2018 12:52:00 GMT

     [ https://issues.apache.org/jira/browse/LUCENE-8123?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Robert Muir resolved LUCENE-8123.
---------------------------------
    Resolution: Invalid

Please use the mailing list for questions.

> 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 between
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", term.bytes()) . After the inner products of these related documents have been computed,
the final similarities are computed by dividing these inner products by their norms.
>     However, when the documents scale up, e.g., more than ten million titles of twitter's
text filed each on average has 10 terms, the runtime is unacceptable (more than ten seconds)
since we always need to merge 0.5~2 million documents to generate the inner products. Does
Lucene provide more efficient interface to generate ranked results based on TFIDF, or directly
filter out the dissimilar documents (in lucene core) for a given threshold in the range of
(0, 1)?
> Best
> Wenhai 



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