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Posted to dev@lucene.apache.org by "David Smiley (JIRA)" <ji...@apache.org> on 2018/10/24 13:49:00 UTC

[jira] [Commented] (LUCENE-8492) UnifiedHighlighter does not work with Surround query parser (SurroundQParser)

    [ https://issues.apache.org/jira/browse/LUCENE-8492?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16662306#comment-16662306 ] 

David Smiley commented on LUCENE-8492:
--------------------------------------

Maybe the UH should actually rewrite the Query up front _if and only if_ the UH's attempt to detect terms/automata etc. found nothing?  Hmmm but its potentially expensive since it'd use the real underlying index, and the query might contain a MTQ.  And the reason we found nothing may be because we only want to highlight some fields that just so happened to not be in the query.  I suppose it should not do this but I wanted to record my thinking here.  Maybe it'd be nice if the UH had a HighlightFlag option to avoid OffsetSource.NONE_NEEDED and instead assume the query might have anything.  But that isn't terribly needed since the user could subclass to override getOptimizedOffsetSource to never return NONE_NEEDED.

Other than SurroundQParser, I wonder if any real-world users have queries that run into this?

> UnifiedHighlighter does not work with Surround query parser (SurroundQParser)
> -----------------------------------------------------------------------------
>
>                 Key: LUCENE-8492
>                 URL: https://issues.apache.org/jira/browse/LUCENE-8492
>             Project: Lucene - Core
>          Issue Type: Bug
>          Components: modules/highlighter
>    Affects Versions: 7.2.1
>            Reporter: Andy Liu
>            Priority: Major
>         Attachments: TestUnifiedHighlighterSurround.java
>
>
> I'm attempting to use the UnifiedHighlighter in conjunction with queries parsed by Solr's SurroundQParserPlugin. When doing so, the response yields empty arrays for documents that should contain highlighted snippets.
> I've attached a test for UnifiedHighlighter that uses the surround's QueryParser and preprocesses the query in a similar fashion as SurroundQParser, which results in test failure.  When creating a SpanQuery directly (rather via surround's QueryParser), the test passes.
> The problem can be isolated to the code path initiated by UnifiedHighlighter.extractTerms(), which uses EMPTY_INDEXSEARCHER to extract terms from the query. After a series of method calls, we end up at DistanceQuery.getSpanNearQuery(), where {{((DistanceSubQuery)sqi.next()).addSpanQueries(sncf)}} fails silently and doesn't add any span queries.  
> Another data point: If I hack UnifiedHighlighter and pass in a live IndexSearcher to extractTerms(), highlighting works. 



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