mgaido91 commented on issue #22450: [SPARK-25454][SQL] Avoid precision loss in 
division with decimal with negative scale
URL: https://github.com/apache/spark/pull/22450#issuecomment-473253706
 
 
   > Can you list some of them?
   
   Oracle for instance allows negative scales.
   
   > we should find out the cases that will be broken, and put them in the 
release notes.
   
   Well, the cases are obvious, ie. when there are negative scales which define 
numbers which don't fit in (38, 0), surely we cannot handle them anymore; 
moreover we need to convert to non-negative all the cases when the users 
provides a scala/java decimal with negative scale and we may cause some 
precision losses in cases when a negative scale and a non-negative one are the 
inputs for an arithmetic operation.
   
   > Personally I'd prefer the first direction, as that's how other mainstream 
databases do.
   
   I agree with you in general, but then when I think to the backward 
compatibility issues I am doubtful about it. And in the discussion in the 
mailing list I think @rxin preferred to avoid these breaking changes too.
   
   > I would reject a proposal that only allows negative scale, as its 
definition will be hard to generalize.
   
   Just to be clear, here I am not proposing to allow negative scales, I am 
just proposing to handle them properly in the operations since they happen to 
be present.

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