Fig. 3From: Robust Cardinality: a novel approach for cardinality prediction in SQL queriesAn example of GBDT’s learners [31]. Each of one is a decision tree that was trained to generate a good prediction illustrated by the blue nodes. All of these predictions are then transformed into a single final prediction through a chosen function, commonly mean or voting. Hence, this final prediction will be used as estimates by the optimizerBack to article page