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https://issues.apache.org/jira/browse/SOLR-5330?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13797244#comment-13797244
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Yonik Seeley commented on SOLR-5330:
------------------------------------

I never was able to reproduce... so I just fixed the issue anyway, making a 
copy of the bytes only instead of cloning the complete BytesRef.

> PerSegmentSingleValuedFaceting overwrites facet values
> ------------------------------------------------------
>
>                 Key: SOLR-5330
>                 URL: https://issues.apache.org/jira/browse/SOLR-5330
>             Project: Solr
>          Issue Type: Bug
>    Affects Versions: 4.2.1
>            Reporter: Michael Froh
>            Assignee: Yonik Seeley
>             Fix For: 4.5.1, 4.6, 5.0
>
>         Attachments: solr-5330.patch
>
>
> I recently tried enabling facet.method=fcs for one of my indexes and found a 
> significant performance improvement (with a large index, many facet values, 
> and near-realtime updates). Unfortunately, the results were also wrong. 
> Specifically, some facet values were being partially overwritten by other 
> facet values. (That is, if I expected facet values like "abcdef" and "123", I 
> would get a value like "123def".)
> Debugging through the code, it looks like the problem was in 
> PerSegmentSingleValuedFaceting, specifically in the getFacetCounts method, 
> when BytesRef val is shallow-copied from the temporary per-segment BytesRef. 
> The byte array assigned to val is shared with the byte array for seg.tempBR, 
> and is overwritten a few lines down by the call to seg.tenum.next().
> I managed to fix it locally by replacing the shallow copy with a deep copy.
> While I encountered this problem on Solr 4.2.1, I see that the code is 
> identical in 4.5. Unless the behavior of TermsEnum.next() has changed, I 
> believe this bug still exists.



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