[GitHub] [spark] cloud-fan commented on issue #21599: [SPARK-26218][SQL] Overflow on arithmetic operations returns incorrect result

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cloud-fan commented on issue #21599: [SPARK-26218][SQL] Overflow on arithmetic operations returns incorrect result
URL: https://github.com/apache/spark/pull/21599#issuecomment-514117978
 
 
   For overflow checking, I do think `Math.addExtract` is better, although it doesn't work for byte/short and float/double.
   1. For byte/short, we add them as int(this is how java adds 2 bytes), and then check if it exceeds the range of byte/short, and then cast it back to byte/short. I think this should be faster than checking the signum.
   2. For float/double, I'm not sure we can check overflow by signum. And float/double can be `Infinity` at the beginning, so I don't really know how to detect overflows. Can you check other databases?
   
   For the interpreted version, we can implement custom `Numeric` in places like `ByteType#numeric` and add overflow check.
   

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