Optimizing the confidence bound of count-min sketches to estimate the streaming big data query results more precisely

A count-min sketch is a probabilistic data structure, which serves as a frequency table of events to process a stream of big data. It uses hash functions to map events to frequencies. Querying a count-min sketch returns the targeted event along with an estimated frequency, which is not less than the actual frequency. The estimated error, i.e., the difference between the estimated frequency and the actual, can be measured by a pre-defined confidence bound. However, the bound originally defined is too loose. The reason is that the Markov inequality used to derive the bound does not perform well. In this paper, based on binomial distribution and central limit theorem, we define a tighter bound. We indicate that the reliability of the bound is related to the deviation of data, which can be measured by the data’s coefficient of standard deviation. Our extensive experiments well support the effectiveness and efficiency of the new bound.