presto-main/src/main/java/io/prestosql/operator/window/CumulativeDistributionFunction.java/CumulativeDistributionFunction/processRow
class CumulativeDistributionFunction:    @Override
    public void processRow(BlockBuilder output, boolean newPeerGroup, int peerGroupCount, int currentPosition)
    {
        if (newPeerGroup) {
            count += peerGroupCount;
        }
        DOUBLE.writeDouble(output, ((double) count) / totalCount);
    }