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From "Otis Gospodnetic (JIRA)" <>
Subject [jira] Updated: (LUCENE-1229) NGramTokenFilter optimization in query phase
Date Sat, 17 May 2008 04:17:55 GMT


Otis Gospodnetic updated LUCENE-1229:

    Lucene Fields: [New, Patch Available]  (was: [Patch Available, New])
         Assignee: Otis Gospodnetic

Let me see if I understand this.  The reason only ab bc de are needed is because we only need
single-sized n-grams in the query, even if the index-time n-grams had a range of sizes (1
and 2 in your example).

I think that makes sense, as long as the positions are right, so that even if we put ab cd
de in a phrase query (e.g. "ab bc de") that matches "a ab b bc c cd d de e".  Is that the

Of course, because this issue contains a patch that includes changes for various other n-gram
issues, I can't just commit this and we have to wait until we resolve other n-gram issues.

> NGramTokenFilter optimization in query phase
> --------------------------------------------
>                 Key: LUCENE-1229
>                 URL:
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: contrib/*
>            Reporter: Hiroaki Kawai
>            Assignee: Otis Gospodnetic
>         Attachments: NGramTokenFilter.patch
> I found that NGramTokenFilter-ed token stream could be optimized in query.
> A standard 1,2 NGramTokenFilter will generate a token stream from "abcde" as follows:
> a ab b bc c cd d de e
> When we index "abcde", we'll use all of the tokens.
> But when we query, we only need:
> ab cd de

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