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https://issues.apache.org/jira/browse/LUCENE-8344?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16500343#comment-16500343
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David Smiley commented on LUCENE-8344:
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To demonstrate the issue in the patch I added a
TokenStreamToAutomaton.BUG boolean flag so a test can see what happens when
the suggest index had trailing holes but differs at query time.
org.apache.lucene.search.suggest.analyzing.AnalyzingSuggesterTest#testStandard
see the "round trip" test
With BUG==true: fails (bad for back-compat)
With BUG==false: passes (therefore a reindex fixes)
org.apache.lucene.search.suggest.document.TestPrefixCompletionQuery#testAnalyzerWithSepAndNoPreservePos
see "test trailing stopword with a new document"
With BUG==true: passes (good for back-compat)
With BUG==false: fails(*)
(*): however if you flip the analyzer passed to the PrefixCompletionQuery
constructor to the "completionAnalyzer" (instead of the plain/original
"analyzer"), then it passes. So apparently this may require users change how
it's used? (ouch)
CC [~areek]
> TokenStreamToAutomaton doesn't ignore trailing posInc when
> preservePositionIncrements=false
> -------------------------------------------------------------------------------------------
>
> Key: LUCENE-8344
> URL: https://issues.apache.org/jira/browse/LUCENE-8344
> Project: Lucene - Core
> Issue Type: Bug
> Components: modules/suggest
> Reporter: David Smiley
> Priority: Major
> Attachments: LUCENE-8344.patch, LUCENE-8344.patch
>
>
> TokenStreamToAutomaton in Lucene core is used by the AnalyzingSuggester
> (incl. FuzzySuggester subclass ) and NRT Document Suggester and soon the
> SolrTextTagger. It has a setting {{preservePositionIncrements}} defaulting
> to true. If it's set to false (e.g. to ignore stopwords) and if there is a
> _trailing_ position increment greater than 1, TS2A will _still_ add position
> increments (holes) into the automata even though it was configured not to.
> I'm filing this issue separate from LUCENE-8332 where I first found it. The
> fix is very simple but I'm concerned about back-compat ramifications so I'm
> filing it separately. I'll attach a patch to show the problem.
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