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Posted to github@arrow.apache.org by "Dandandan (via GitHub)" <gi...@apache.org> on 2023/02/01 09:41:03 UTC

[GitHub] [arrow-rs] Dandandan opened a new issue, #3645: Multiplication for decimals is incorrect

Dandandan opened a new issue, #3645:
URL: https://github.com/apache/arrow-rs/issues/3645

   **Describe the bug**
   Multiplication for decimals is wrong for decimals 
   
   **To Reproduce**
   <!--
   Steps to reproduce the behavior:
   -->
   
   ```
       #[test]
       fn test_decimal_multiplication() {
           let a = Decimal128Array::from_iter_values([1]).with_precision_and_scale(1, 1).unwrap();
           
           let b = Decimal128Array::from_iter_values([1]).with_precision_and_scale(1, 1).unwrap();
   
           let e = Decimal128Array::from_iter_values([1]).with_precision_and_scale(2, 2).unwrap();
           let r = multiply(&a, &b).unwrap();
           assert_eq!(e, r);
       }
   ```
   0.1 * 0.1 should return 0.01.
   
   The current kernel just multiplies the raw integers but ignores the scale/precision values of the.
   
   ```
     left: `PrimitiveArray<Decimal128(2, 2)>
   [
     1,
   ]`,
    right: `PrimitiveArray<Decimal128(38, 10)>
   [
     1,
   ]`', arrow-arith/src/arithmetic.rs:2958:9
   
   ```
   
   **Expected behavior**
   The kernel should add scale as well, values 0.1 * 0.1 should have primitive value `1` with scale `2`.
   
   **Additional context**
   <!--
   Add any other context about the problem here.
   -->


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[GitHub] [arrow-rs] Dandandan commented on issue #3645: Multiplication for decimals is incorrect

Posted by "Dandandan (via GitHub)" <gi...@apache.org>.
Dandandan commented on issue #3645:
URL: https://github.com/apache/arrow-rs/issues/3645#issuecomment-1411771779

   Probably we don't expect the kernels in arrow-rs to handle this (but should do it in datafusion).


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[GitHub] [arrow-rs] Dandandan closed issue #3645: Multiplication for decimals is incorrect

Posted by "Dandandan (via GitHub)" <gi...@apache.org>.
Dandandan closed issue #3645: Multiplication for decimals is incorrect
URL: https://github.com/apache/arrow-rs/issues/3645


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