[GitHub] [druid] minkedong commented on issue #10519: When I use topN query, the results are very different.

[GitBox <gi...@apache.org>]

minkedong commented on issue #10519:
URL: https://github.com/apache/druid/issues/10519#issuecomment-719326525


   > For TopN, query engine collect top 1000(by default) ordered result from each segment, then merge all results to determine the global top 1000. For example, a data source has two segment A,B, for your second query, segment A, B contains value of (bundle, traffic) respectively (1115565187, 20) ranking 49 and (1115565187, 40) ranking 51, because of threshold = 50, query engine only collect result of segment A, result of B drop, which is approximate. But for your first query with filter, segment A, B contains value of (bundle, traffic) respectively (1115565187, 20) ranking 1 and (1115565187, 40) ranking 1 , result collected is accurate. if you need accurate result of your second query, try to increase threshold.
   
   @zoov-w Thank you very much for your answer, Your answer helped me solve the problem and at the same time let me understand the cause of the problem, great!
   


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