Distinct-Values Estimation over Data Streams

Abstract

In this chapter, we consider the problem of estimating the number of distinct values in a data stream with repeated values. Distinct- values estimation was one of the first data stream problems studied: In the mid-1980’s, Flajolet and Martin gave an effective algorithm that uses only logarithmic space. Recent work has built upon their tech- nique, improving the accuracy guarantees on the estimation, proving lower bounds, and considering other settings such as sliding windows, distributed streams, and sensor networks.