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Posted to github@arrow.apache.org by "tustvold (via GitHub)" <gi...@apache.org> on 2023/06/29 13:15:38 UTC
[GitHub] [arrow-datafusion] tustvold opened a new pull request, #6797: Remove fixed point decimal arithmetic
tustvold opened a new pull request, #6797:
URL: https://github.com/apache/arrow-datafusion/pull/6797
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# Rationale for this change
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This logic was added in https://github.com/apache/arrow-datafusion/pull/6103, however, I can't see how it would be used. I tried removing it and no tests failed, so I'm now just a little bit confused... Can this just be removed? As an added bonus this will be significantly faster...
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[GitHub] [arrow-datafusion] tustvold commented on a diff in pull request #6797: Remove fixed point decimal arithmetic
Posted by "tustvold (via GitHub)" <gi...@apache.org>.
tustvold commented on code in PR #6797:
URL: https://github.com/apache/arrow-datafusion/pull/6797#discussion_r1246606928
##########
datafusion/physical-expr/src/expressions/binary/kernels_arrow.rs:
##########
@@ -698,152 +692,13 @@ pub(crate) fn subtract_dyn_decimal(
decimal_array_with_precision_scale(array, precision, scale)
}
-/// Remove this once arrow-rs provides `multiply_fixed_point_dyn`.
-fn math_op_dict<K, T, F>(
- left: &DictionaryArray<K>,
- right: &DictionaryArray<K>,
- op: F,
-) -> Result<PrimitiveArray<T>>
-where
- K: ArrowDictionaryKeyType + ArrowNumericType,
- T: ArrowNumericType,
- F: Fn(T::Native, T::Native) -> T::Native,
-{
- if left.len() != right.len() {
- return Err(DataFusionError::Internal(format!(
- "Cannot perform operation on arrays of different length ({}, {})",
- left.len(),
- right.len()
- )));
- }
-
- // Safety justification: Since the inputs are valid Arrow arrays, all values are
- // valid indexes into the dictionary (which is verified during construction)
-
- let left_iter = unsafe {
- left.values()
- .as_primitive::<T>()
- .take_iter_unchecked(left.keys_iter())
- };
-
- let right_iter = unsafe {
- right
- .values()
- .as_primitive::<T>()
- .take_iter_unchecked(right.keys_iter())
- };
-
- let result = left_iter
- .zip(right_iter)
- .map(|(left_value, right_value)| {
- if let (Some(left), Some(right)) = (left_value, right_value) {
- Some(op(left, right))
- } else {
- None
- }
- })
- .collect();
-
- Ok(result)
-}
-
-/// Divide a decimal native value by given divisor and round the result.
-/// Remove this once arrow-rs provides `multiply_fixed_point_dyn`.
-fn divide_and_round<I>(input: I::Native, div: I::Native) -> I::Native
-where
- I: DecimalType,
- I::Native: ArrowNativeTypeOp,
-{
- let d = input.div_wrapping(div);
- let r = input.mod_wrapping(div);
-
- let half = div.div_wrapping(I::Native::from_usize(2).unwrap());
- let half_neg = half.neg_wrapping();
- // Round result
- match input >= I::Native::ZERO {
- true if r >= half => d.add_wrapping(I::Native::ONE),
- false if r <= half_neg => d.sub_wrapping(I::Native::ONE),
- _ => d,
- }
-}
-
-/// Remove this once arrow-rs provides `multiply_fixed_point_dyn`.
-/// <https://github.com/apache/arrow-rs/issues/4135>
-fn multiply_fixed_point_dyn(
- left: &dyn Array,
- right: &dyn Array,
- required_scale: i8,
-) -> Result<ArrayRef> {
- match (left.data_type(), right.data_type()) {
- (
- DataType::Dictionary(_, lhs_value_type),
- DataType::Dictionary(_, rhs_value_type),
- ) if matches!(lhs_value_type.as_ref(), &DataType::Decimal128(_, _))
- && matches!(rhs_value_type.as_ref(), &DataType::Decimal128(_, _)) =>
- {
- downcast_dictionary_array!(
- left => match left.values().data_type() {
- DataType::Decimal128(_, _) => {
- let lhs_precision_scale = get_precision_scale(lhs_value_type.as_ref())?;
- let rhs_precision_scale = get_precision_scale(rhs_value_type.as_ref())?;
-
- let product_scale = lhs_precision_scale.1 + rhs_precision_scale.1;
- let precision = min(lhs_precision_scale.0 + rhs_precision_scale.0 + 1, DECIMAL128_MAX_PRECISION);
-
- if required_scale == product_scale {
- return Ok(multiply_dyn(left, right)?.as_primitive::<Decimal128Type>().clone()
- .with_precision_and_scale(precision, required_scale).map(|a| Arc::new(a) as ArrayRef)?);
- }
-
- if required_scale > product_scale {
- return Err(DataFusionError::Internal(format!(
- "Required scale {required_scale} is greater than product scale {product_scale}"
- )));
- }
-
- let divisor =
- i256::from_i128(10).pow_wrapping((product_scale - required_scale) as u32);
-
- let right = as_dictionary_array::<_>(right);
-
- let array = math_op_dict::<_, Decimal128Type, _>(left, right, |a, b| {
- let a = i256::from_i128(a);
- let b = i256::from_i128(b);
-
- let mut mul = a.wrapping_mul(b);
- mul = divide_and_round::<Decimal256Type>(mul, divisor);
- mul.as_i128()
- }).map(|a| a.with_precision_and_scale(precision, required_scale).unwrap())?;
-
- Ok(Arc::new(array))
- }
- t => unreachable!("Unsupported dictionary value type {}", t),
- },
- t => unreachable!("Unsupported data type {}", t),
- )
- }
- (DataType::Decimal128(_, _), DataType::Decimal128(_, _)) => {
- let left = left.as_any().downcast_ref::<Decimal128Array>().unwrap();
- let right = right.as_any().downcast_ref::<Decimal128Array>().unwrap();
-
- Ok(multiply_fixed_point(left, right, required_scale)
- .map(|a| Arc::new(a) as ArrayRef)?)
- }
- (_, _) => Err(DataFusionError::Internal(format!(
- "Unsupported data type {}, {}",
- left.data_type(),
- right.data_type()
- ))),
- }
-}
-
pub(crate) fn multiply_dyn_decimal(
left: &dyn Array,
right: &dyn Array,
result_type: &DataType,
) -> Result<ArrayRef> {
let (precision, scale) = get_precision_scale(result_type)?;
- let array = multiply_fixed_point_dyn(left, right, scale)?;
Review Comment:
This also makes it consistent with `multiply_decimal_dyn_scalar` - https://github.com/apache/arrow-datafusion/pull/6797/files#diff-133624520f20c20b33c2c54ec6ae565f09b058ef317ede0e768bd23bae30941dL667
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[GitHub] [arrow-datafusion] tustvold closed pull request #6797: Remove fixed point decimal arithmetic
Posted by "tustvold (via GitHub)" <gi...@apache.org>.
tustvold closed pull request #6797: Remove fixed point decimal arithmetic
URL: https://github.com/apache/arrow-datafusion/pull/6797
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[GitHub] [arrow-datafusion] viirya commented on pull request #6797: Remove fixed point decimal arithmetic
Posted by "viirya (via GitHub)" <gi...@apache.org>.
viirya commented on PR #6797:
URL: https://github.com/apache/arrow-datafusion/pull/6797#issuecomment-1613661190
It was added with a test modified. I'm not sure why no tests failed now. As it is two months ago, there might be some changes I don't follow up.
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[GitHub] [arrow-datafusion] tustvold commented on pull request #6797: Remove fixed point decimal arithmetic
Posted by "tustvold (via GitHub)" <gi...@apache.org>.
tustvold commented on PR #6797:
URL: https://github.com/apache/arrow-datafusion/pull/6797#issuecomment-1613170838
Oh I see why this exists, the type coercion logic will clamp the scale to the maximum for the type, and we then need to perform a truncating multiply to handle this :+1:
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