Function get_scale

datafusion/spark/src/function/math/round.rs:130–165

Extract the scale (decimal places) from the second argument. Returns `Some(0)` if no second argument is provided. Returns `None` if the scale argument is NULL (Spark returns NULL for `round(expr, NULL)`).

(args: &[ColumnarValue])

/// Returns `Some(0)` if no second argument is provided.
/// Returns `None` if the scale argument is NULL (Spark returns NULL for `round(expr, NULL)`).
fn get_scale(args: &[ColumnarValue]) -> Result<Option<i32>> {
    if args.len() < 2 {
        return Ok(Some(0));
    }

    match &args[1] {
        ColumnarValue::Scalar(ScalarValue::Int8(Some(v))) => Ok(Some(i32::from(*v))),
        ColumnarValue::Scalar(ScalarValue::Int16(Some(v))) => Ok(Some(i32::from(*v))),
        ColumnarValue::Scalar(ScalarValue::Int32(Some(v))) => Ok(Some(*v)),
        ColumnarValue::Scalar(ScalarValue::Int64(Some(v))) => {
            i32::try_from(*v).map(Some).map_err(|_| {
                (exec_err!("round scale {v} is out of supported i32 range")
                    as Result<(), _>)
                    .unwrap_err()
            })
        }
        ColumnarValue::Scalar(ScalarValue::UInt8(Some(v))) => Ok(Some(i32::from(*v))),
        ColumnarValue::Scalar(ScalarValue::UInt16(Some(v))) => Ok(Some(i32::from(*v))),
        ColumnarValue::Scalar(ScalarValue::UInt32(Some(v))) => {
            i32::try_from(*v).map(Some).map_err(|_| {
                (exec_err!("round scale {v} is out of supported i32 range")
                    as Result<(), _>)
                    .unwrap_err()
            })
        }
        ColumnarValue::Scalar(ScalarValue::UInt64(Some(v))) => {
            i32::try_from(*v).map(Some).map_err(|_| {
                (exec_err!("round scale {v} is out of supported i32 range")
                    as Result<(), _>)
                    .unwrap_err()
            })
        }
        ColumnarValue::Scalar(sv) if sv.is_null() => Ok(None),
        other => exec_err!("Unsupported type for round scale: {}", other.data_type()),
    }
}

/// Round a floating-point value to the given number of decimal places using
/// HALF_UP rounding mode (ties round away from zero).