tustvold commented on code in PR #2770:
URL: https://github.com/apache/arrow-rs/pull/2770#discussion_r978435034
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arrow/src/compute/kernels/arithmetic.rs:
##########
@@ -1605,6 +1605,168 @@ where
unary_dyn::<_, T>(array, |value| value.div_wrapping(divisor))
}
+/// Creates an Decimal128Array the same size as `left`,
+/// by applying `op` to all non-null elements of left and right
+fn arith_decimal<F>(
+ left: &Decimal128Array,
+ right: &Decimal128Array,
+ op: F,
+) -> Result<Decimal128Array>
+where
+ F: Fn(i128, i128) -> Result<i128>,
+{
+ left.iter()
+ .zip(right.iter())
+ .map(|(left, right)| {
+ if let (Some(left), Some(right)) = (left, right) {
+ Some(op(left.as_i128(), right.as_i128())).transpose()
+ } else {
+ Ok(None)
+ }
+ })
+ .collect()
+}
+
+fn arith_decimal_scalar<F>(
+ left: &Decimal128Array,
+ right: i128,
+ op: F,
+) -> Result<Decimal128Array>
+where
+ F: Fn(i128, i128) -> Result<i128>,
+{
+ left.iter()
+ .map(|left| {
+ if let Some(left) = left {
+ Some(op(left.as_i128(), right)).transpose()
+ } else {
+ Ok(None)
+ }
+ })
+ .collect()
+}
+
+pub fn add_decimal(
+ left: &Decimal128Array,
+ right: &Decimal128Array,
+) -> Result<Decimal128Array> {
+ let array = arith_decimal(left, right, |left, right| Ok(left + right))?
+ .with_precision_and_scale(left.precision(), left.scale())?;
+ Ok(array)
+}
+
+pub fn add_decimal_scalar(
+ left: &Decimal128Array,
+ right: i128,
+) -> Result<Decimal128Array> {
+ let array = arith_decimal_scalar(left, right, |left, right| Ok(left +
right))?
+ .with_precision_and_scale(left.precision(), left.scale())?;
+ Ok(array)
+}
+
+pub fn subtract_decimal(
+ left: &Decimal128Array,
+ right: &Decimal128Array,
+) -> Result<Decimal128Array> {
+ let array = arith_decimal(left, right, |left, right| Ok(left - right))?
+ .with_precision_and_scale(left.precision(), left.scale())?;
+ Ok(array)
+}
+
+pub fn subtract_decimal_scalar(
+ left: &Decimal128Array,
+ right: i128,
+) -> Result<Decimal128Array> {
+ let array = arith_decimal_scalar(left, right, |left, right| Ok(left -
right))?
+ .with_precision_and_scale(left.precision(), left.scale())?;
+ Ok(array)
+}
+
+pub fn multiply_decimal(
+ left: &Decimal128Array,
+ right: &Decimal128Array,
+) -> Result<Decimal128Array> {
+ let divide = 10_i128.pow(left.scale() as u32);
+ let array = arith_decimal(left, right, |left, right| {
+ let result = BigInt::from(left) * BigInt::from(right) / divide;
+ Ok(result.to_i128().unwrap())
+ })?
+ .with_precision_and_scale(left.precision(), left.scale())?;
+ Ok(array)
+}
+
+pub fn multiply_decimal_scalar(
+ left: &Decimal128Array,
+ right: i128,
+) -> Result<Decimal128Array> {
+ let divide = 10_i128.pow(left.scale() as u32);
+ let array = arith_decimal_scalar(left, right, |left, right| {
+ let result = BigInt::from(left) * BigInt::from(right) / divide;
Review Comment:
Why can't we use i128 for this? The performance should be better than a
variable width encoding?
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