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Posted to commits@druid.apache.org by "kgyrtkirk (via GitHub)" <gi...@apache.org> on 2023/12/11 14:20:55 UTC

[I] ResultsCache may cause ClassCastException-s in case a sketch is stored in the cache (druid)

kgyrtkirk opened a new issue, #15538:
URL: https://github.com/apache/druid/issues/15538

   <details>
   <summary>when resultscache is enabled</summary>
   
   ```
   cat >> conf/druid/auto/broker/runtime.properties  <<EOF
   druid.broker.cache.useResultLevelCache=true
   druid.broker.cache.populateResultLevelCache=true
   EOF
   ```
   
   A query which may store a sketch in the resultscache:
   
   </details>
   
   ```
   SELECT  TIME_FLOOR(__time, 'P1D') as dayLvl,
     dim1,
     HLL_SKETCH_ESTIMATE(DS_HLL(hllsketch_dim1,18,'HLL_4'), true),
     HLL_SKETCH_ESTIMATE(DS_HLL(DS_HLL(hllsketch_dim1,18,'HLL_4'),18,'HLL_4') OVER (PARTITION BY dim1), true),  1
   FROM
     (select * from  druid.foo ) ttt
     WHERE  __time >= '1903-08-02' AND __time <= '2033-08-07'
     and dim1 not like '%ikipedia' and l1 > -4
     group by 1,2
   ```
   
   after the first successfull execution (no cache hit) results in: 
   ```
   Unknown exception: class [B cannot be cast to class org.apache.druid.query.aggregation.datasketches.hll.HllSketchHolder ([B is in module java.base of loader 'bootstrap'; org.apache.druid.query.aggregation.datasketches.hll.HllSketchHolder is in unnamed module of loader java.net.URLClassLoader @348ad293)
   ```
   
   note: it could happen with windowing queries; however it can be reproduced even without that.
   
   workaround could be to disable the usage of the resultscache


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Re: [I] ResultsCache may cause ClassCastException-s in case a sketch is stored in the cache (druid)

Posted by "rohangarg (via GitHub)" <gi...@apache.org>.
rohangarg closed issue #15538: ResultsCache may cause ClassCastException-s in case a sketch is stored in the cache
URL: https://github.com/apache/druid/issues/15538


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