Quantifying uncertainty in multi-dimensional cardinality estimations

Abstract

We propose a method for predicting the cardinality distribution of a multi-dimensional query. Compared to conventional 'point-based' estimates, distribution-based estimates enable the query optimizer to predict the cost of a query plan more accurately, as we show experimentally. Our method is computationally efficient and works on top of a histogram already in place. It does not store any information additional to the histogram. Our experiments show that the quality of the predictions with the new method is high.