1. A computer-implemented method of counting predictor-target pairs for a decision tree model, the decision tree model based on data stored in a database, the data comprising a plurality of rows of data, at least one predictor and at least one target, the method comprising: generating a split node bitmap for each tree node corresponding to a subset of data stored in a database system by intersecting a parent node bitmap and a bitmap of a predictor that satisfies a condition of the node; intersecting each split node bitmap with each predictor bitmap and with each target bitmap to form intersected bitmaps; and counting bits of each intersected bitmap to generate a count of per-node predictor-target pairs.