Github user HyukjinKwon commented on the pull request:

    https://github.com/apache/spark/pull/8718#issuecomment-141960719
  
    It looks the original case became a downcast `Decimal(10, 0)` to 
`Decimal(7, 2)` which seems when scale and precision of the latter are less 
than the former, rather than int to decimal. I think there have been an update 
at Optimizer.
    
    It looks roughly in most cases, the conversions need to be downcasted. 
    Here is a list i tested.
    
    1. Where `A` is `IntegerType`
    `WHERE A <= 2500` becomes int to int
    `WHERE A <= 2500.0` becomes decimal(11, 1) to decimal(10, 0)
    
    2. Where `A` is `Decimal(7,2)`
    `WHERE A <= 2500` becomes decimal(10, 0) to decimal(7, 2)
    `WHERE A <= 2500.0` becomes decimal(7, 2) to decimal(7, 2)
    `WHERE A <= 2500.00` becomes decimal(12, 2) to decimal(7, 2)
    
    3. Where `A` is `Double`
    `WHERE A <= 2500` becomes double to double
    `WHERE A <= 2500.0` becomes double to double
    
    So I think even if I check the widening cast dealing with types and both 
precision and scale in `Decimal`, neither this issue can be resolved nor deals 
with a lot of use-cases.
    
    I'm not too sure if 
    1. I should just go for this
    2. handles only numbers including downcasts with `Cast(...).eval()`, or 
    3. just close this. 


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