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From "Michael McCandless (JIRA)" <>
Subject [jira] [Created] (LUCENE-4481) AnalyzingSuggester may fail to return correct topN suggestions
Date Fri, 12 Oct 2012 15:15:04 GMT
Michael McCandless created LUCENE-4481:

             Summary: AnalyzingSuggester may fail to return correct topN suggestions
                 Key: LUCENE-4481
             Project: Lucene - Core
          Issue Type: Bug
            Reporter: Michael McCandless
             Fix For: 4.1, 5.0

I hit this when working on LUCENE-4480.

Because AnalyzingSuggester may prune some of the topN paths found by FST's Util.TopNSearcher,
this means the queue size limit of topN makes the overall search inadmissible, ie it may incorrectly
prune paths that would have lead to a competitive path.

However, such pruning is rare: it happens only for graph token streams, and even then only
when competitive analyzed forms share the same surface forms.

The simplest way to fix this is to make the queue unbounded but this is likely a sizable performance
hit ... I haven't tested yet.  It's even possible the way the dups happen (always at the "end"
of the suggestion, because we tack on 0 byte followed by ord dedup byte) prevent this bug
from even occurring and so this could all be a false alarm!  I have to try to make a test
case showing it ...

A cop-out solution would be to expose a separate queueSize or queueMultiplier (over the topN)
so that if users are affected by this they could crank up the queue size or multiplier.

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