[GitHub] [druid] Kinigopoulos commented on issue #11267: Cannot create a new extension query that executes successfully

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Kinigopoulos commented on issue #11267:
URL: https://github.com/apache/druid/issues/11267#issuecomment-842913033


   @FrankChen021 thanks for the reply.
   
   My plan was to follow the moving average as an example but it does not contain any implementation for RunnerFactory so it doesn't process the segments itself (although I wouldn't mind taking the data from a groupBy query and edit them from there) but also has that issue (#11266) with ClassCastException
   
   The NPE is being thrown by the Druid code:
   ```
   at com.google.common.base.Preconditions.checkNotNull(Preconditions.java:229)
   	at org.apache.druid.query.Query.getMostSpecificId(Query.java:172)
   	at org.apache.druid.client.CachingClusteredClient.initializeNumRemainingResponsesInResponseContext(CachingClusteredClient.java:217)
   	at org.apache.druid.client.CachingClusteredClient.run(CachingClusteredClient.java:205)
   	at org.apache.druid.client.CachingClusteredClient.access$100(CachingClusteredClient.java:116)
   	at org.apache.druid.client.CachingClusteredClient$2.run(CachingClusteredClient.java:187)
   	at org.apache.druid.query.RetryQueryRunner.run(RetryQueryRunner.java:108)
   	at org.apache.druid.server.SetAndVerifyContextQueryRunner.run(SetAndVerifyContextQueryRunner.java:51)
   	at org.apache.druid.query.UnionQueryRunner.run(UnionQueryRunner.java:92)
   	at org.apache.druid.query.ResultMergeQueryRunner.doRun(ResultMergeQueryRunner.java:58)
   	at org.apache.druid.query.BySegmentSkippingQueryRunner.run(BySegmentSkippingQueryRunner.java:46)
   	at org.apache.druid.query.FinalizeResultsQueryRunner.run(FinalizeResultsQueryRunner.java:110)
   	at org.apache.druid.query.CPUTimeMetricQueryRunner.run(CPUTimeMetricQueryRunner.java:65)
   	at org.apache.druid.query.ResultLevelCachingQueryRunner.run(ResultLevelCachingQueryRunner.java:158)
   	at org.apache.druid.query.FluentQueryRunnerBuilder$FluentQueryRunner.run(FluentQueryRunnerBuilder.java:55)
   	at org.apache.druid.server.ClientQuerySegmentWalker$QuerySwappingQueryRunner.run(ClientQuerySegmentWalker.java:511)
   	at org.apache.druid.query.QueryRunner.run(QueryRunner.java:38)
   ```
   
   If I include this piece of code below in QueryToolChest, then the query runs with no errors and returns an empty result but no runners are getting created from the RunnerFactory so basically the problem isn't resolved.
   ```
     @Override
     public QueryRunner<MapBasedRow> mergeResults(QueryRunner<Row> runner) {
         return (queryPlus, responseContext) -> {
             return Sequences.empty();
         };
     }
   ```


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