Flattened Exponential Histogram for Sliding Window Queries over Data Streams

The Basic Counting problem [1] is one of the most fundamental and critical streaming problems of sliding window queries over data streams. Given a stream of 0's and 1's, the purpose of this problem is to estimate the number of 1's in the last N elements (or time units) seen from the stream. Its solution can be used as building blocks to solve numerous more complex problems such as heavy hitter, frequency estimation, distinct counting, etc. In this paper, we present the flattened exponential histogram (FEH) model for the Basic Counting problem. Our model improves over the exponential histogram [1], [2], a well-received deterministic technique for Basic Counting problem, with respect to accuracy and memory utilization most of the time in practice. Extensive experimental results on real-world datasets show that with the same memory footprint, the accuracy of our model is between 4 to 15 and on average 7 times better than that of the exponential histogram, while the speed is roughly the same.