Exactness, Real Time, and Big DataExactnessReal-Time ProcessingBig DataThe Exactness, Real-Time, and Big Data triangleBig Data and Real TimeApproximation AlgorithmsHashing and Sketching: An IntroductionCounting Distinct Elements: HyperLogLogRole-Playing Exercise: If We Were a System AdministratorPractical HyperLogLog in SparkCounting Element Frequency: Count Min SketchesIntroducing Bloom FiltersBloom Filters with SparkComputing Frequencies with a Count-Min SketchRanks and Quantiles: T-DigestT-Digest in SparkReducing the Number of Elements: SamplingRandom SamplingStratified Sampling