presto-main/src/main/java/io/prestosql/operator/scalar/MathFunctions.java/MathFunctions/floorInteger
class MathFunctions:    @Description("round down to nearest integer")
    @ScalarFunction("floor")
    @SqlType(StandardTypes.INTEGER)
    public static long floorInteger(@SqlType(StandardTypes.INTEGER) long num)
    {
        return num;
    }