[GitHub] [incubator-druid] quenlang commented on issue #7297: thetaSketch aggrgator handle null or "" into unexpected value at ingesting

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quenlang commented on issue #7297: thetaSketch aggrgator handle null or "" into unexpected value at ingesting 
URL: https://github.com/apache/incubator-druid/issues/7297#issuecomment-474497181
 
 
   Thanks for quick reply !
   > Theta sketch ignores nulls and empty strings. Are you sure your input is really empty, not, say, strings with some spaces in them?
   
   Yes, i am sure my input is really empty strings or null, and i also try to perform a query with the HLLSketchMerge aggrgator on the same orignal data but ingested with the HLLSketchBuild aggrgator and druid return 0 from me.
   So i guess  maybe there are some different points between HLL and Theta handle null and empty strings. also maybe it is my mistake in using the ThetaSketch. Can you give me some advices to find out what caused it?
   
   > Regarding the difference between Theta and HLL. You can chose accuracy you wish. Assuming the same accuracy, HLL sketches are substantially smaller than Theta, but don't support set operations (intersection and set difference), and may be slower to merge (union).
   
   Assuming the same accuracy, does HLL use more memroy than Theta during ingesting?

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