[jira] [Created] (SOLR-5330) PerSegmentSingleValuedFaceting overwrites facet values

["Michael Froh (JIRA)" <ji...@apache.org>]

Michael Froh created SOLR-5330:
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             Summary: 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


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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