tustvold commented on code in PR #3690:
URL: https://github.com/apache/arrow-rs/pull/3690#discussion_r1136292121
##########
arrow-arith/src/arithmetic.rs:
##########
@@ -1165,6 +1167,77 @@ pub fn multiply_dyn_checked(
}
}
+/// Perform `left * right` operation on two decimal arrays. If either left or
right value is
+/// null then the result is also null.
+///
+/// This performs decimal multiplication which allows precision loss if an
exact representation
+/// is not possible for the result, according to the required scale. In the
case, the result
+/// will be rounded to the required scale.
+///
+/// It is implemented for compatibility with precision loss `multiply`
function provided by
+/// other data processing engines. For multiplication with precision loss
detection, use
+/// `multiply` or `multiply_checked` instead.
+pub fn mul_fixed_point_checked(
+ left: &PrimitiveArray<Decimal128Type>,
+ right: &PrimitiveArray<Decimal128Type>,
+ required_scale: i8,
+) -> Result<ArrayRef, ArrowError> {
+ let precision = left.precision();
+ let product_scale = left.scale() + right.scale();
+
+ try_binary::<_, _, _, Decimal128Type>(left, right, |a, b| {
+ let a = i256::from_i128(a);
+ let b = i256::from_i128(b);
+
+ a.checked_mul(b)
+ .map(|mut a| {
+ if required_scale < product_scale {
Review Comment:
What happens if required_scale is greater than product_scale, should we just
assert?
##########
arrow-arith/src/arithmetic.rs:
##########
@@ -1165,6 +1167,77 @@ pub fn multiply_dyn_checked(
}
}
+/// Perform `left * right` operation on two decimal arrays. If either left or
right value is
+/// null then the result is also null.
+///
+/// This performs decimal multiplication which allows precision loss if an
exact representation
+/// is not possible for the result, according to the required scale. In the
case, the result
+/// will be rounded to the required scale.
+///
+/// It is implemented for compatibility with precision loss `multiply`
function provided by
+/// other data processing engines. For multiplication with precision loss
detection, use
+/// `multiply` or `multiply_checked` instead.
+pub fn mul_fixed_point_checked(
+ left: &PrimitiveArray<Decimal128Type>,
+ right: &PrimitiveArray<Decimal128Type>,
+ required_scale: i8,
+) -> Result<ArrayRef, ArrowError> {
+ let precision = left.precision();
+ let product_scale = left.scale() + right.scale();
+
+ try_binary::<_, _, _, Decimal128Type>(left, right, |a, b| {
+ let a = i256::from_i128(a);
+ let b = i256::from_i128(b);
+
+ a.checked_mul(b)
Review Comment:
Does this need to be checked, I don't think it can overflow?
##########
arrow-arith/src/arithmetic.rs:
##########
@@ -1165,6 +1167,77 @@ pub fn multiply_dyn_checked(
}
}
+/// Perform `left * right` operation on two decimal arrays. If either left or
right value is
+/// null then the result is also null.
+///
+/// This performs decimal multiplication which allows precision loss if an
exact representation
+/// is not possible for the result, according to the required scale. In the
case, the result
+/// will be rounded to the required scale.
+///
+/// It is implemented for compatibility with precision loss `multiply`
function provided by
+/// other data processing engines. For multiplication with precision loss
detection, use
+/// `multiply` or `multiply_checked` instead.
+pub fn mul_fixed_point_checked(
+ left: &PrimitiveArray<Decimal128Type>,
+ right: &PrimitiveArray<Decimal128Type>,
+ required_scale: i8,
+) -> Result<ArrayRef, ArrowError> {
+ let precision = left.precision();
+ let product_scale = left.scale() + right.scale();
+
+ try_binary::<_, _, _, Decimal128Type>(left, right, |a, b| {
+ let a = i256::from_i128(a);
+ let b = i256::from_i128(b);
+
+ a.checked_mul(b)
+ .map(|mut a| {
+ if required_scale < product_scale {
+ let divisor = i256::from_i128(10)
Review Comment:
I think computing this could be lifted out of the try_unary?
##########
arrow-arith/src/arity.rs:
##########
@@ -77,7 +77,7 @@ pub fn try_unary<I, F, O>(
where
I: ArrowPrimitiveType,
O: ArrowPrimitiveType,
- F: Fn(I::Native) -> Result<O::Native, ArrowError>,
+ F: FnMut(I::Native) -> Result<O::Native, ArrowError>,
Review Comment:
Do we still need these FnMut changes?
##########
arrow-arith/src/arithmetic.rs:
##########
@@ -1165,6 +1167,77 @@ pub fn multiply_dyn_checked(
}
}
+/// Perform `left * right` operation on two decimal arrays. If either left or
right value is
+/// null then the result is also null.
+///
+/// This performs decimal multiplication which allows precision loss if an
exact representation
+/// is not possible for the result, according to the required scale. In the
case, the result
+/// will be rounded to the required scale.
+///
+/// It is implemented for compatibility with precision loss `multiply`
function provided by
+/// other data processing engines. For multiplication with precision loss
detection, use
+/// `multiply` or `multiply_checked` instead.
+pub fn mul_fixed_point_checked(
+ left: &PrimitiveArray<Decimal128Type>,
+ right: &PrimitiveArray<Decimal128Type>,
+ required_scale: i8,
+) -> Result<ArrayRef, ArrowError> {
+ let precision = left.precision();
+ let product_scale = left.scale() + right.scale();
+
+ try_binary::<_, _, _, Decimal128Type>(left, right, |a, b| {
+ let a = i256::from_i128(a);
+ let b = i256::from_i128(b);
+
+ a.checked_mul(b)
+ .map(|mut a| {
+ if required_scale < product_scale {
+ let divisor = i256::from_i128(10)
+ .pow_wrapping((product_scale - required_scale) as u32);
+ a = divide_and_round::<Decimal256Type>(a, divisor);
+ }
+ a
+ })
+ .ok_or_else(|| {
+ ArrowError::ComputeError(format!(
+ "Overflow happened on: {:?} * {:?}, {:?}",
+ a,
+ b,
+ a.checked_mul(b)
+ ))
+ })
+ .and_then(|a| {
Review Comment:
The ? operator may be more legible than chaining and_then
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