[GitHub] [druid] richardstartin commented on issue #9920: Druid 0.13 ~ 0.18 version roaringbitmap benchmark becomes slow

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

richardstartin commented on issue #9920:
URL: https://github.com/apache/druid/issues/9920#issuecomment-633717928


   The code change in #6764 aimed to improve the performance of bitmap construction, and it applies run compression as the bitmap is built, but only to containers which are run-compressible. If this results in slower intersections in some cases, this can be fixed in the RoaringBitmap library; some changes were recently made to significantly improve run vs bitmap `andCardinality` and `intersects` and these changes are applicable to run vs bitmap `and`. 
   
   Note that #6764 will not have changed any behaviour when the roaring bitmaps have been memory mapped from disk and where run compression has already been applied (immediately before construction), which might explain if no regression has otherwise come to light since the change...


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