mirror of https://github.com/apache/druid.git
f684df4c22
* Use an HllSketchHolder object to enable optimized merge HllSketchAggregatorFactory.combine had been implemented using a pure pair-wise, "make a union -> add 2 things to union -> get sketch" algorithm. This algorithm does 2 things that was CPU 1) The Union object always builds an HLL_8 sketch regardless of the target type. This means that when the target type is not HLL_8, we spent CPU cycles converting to HLL_8 and back over and over again 2) By throwing away the Union object and converting back to the HllSketch only to build another Union object, we do lots and lots of copy+conversions of the HllSketch This change introduces an HllSketchHolder object which can hold onto a Union object and delay conversion back into an HllSketch until it is actually needed. This follows the same pattern as the SketchHolder object for theta sketches. |
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README.md
This module provides Druid aggregators based on https://datasketches.apache.org/.
Credits: This module is a result of feedback and work done by following people.
https://github.com/cheddar https://github.com/himanshug https://github.com/leerho https://github.com/will-lauer