[GitHub] [spark] AngersZhuuuu commented on pull request #30350: [SPARK-33428][SQL] Conv UDF use BigInt to avoid Long value overflow

[GitBox <gi...@apache.org>]

AngersZhuuuu commented on pull request #30350:
URL: https://github.com/apache/spark/pull/30350#issuecomment-799894002


   > I found a behavior change here.
   > 
   > Before this commit
   > 
   > ```
   > scala> sql("select conv(-100, 10, 10)").show(20, false)
   > +----------------------------------+
   > |conv(CAST(-100 AS STRING), 10, 10)|
   > +----------------------------------+
   > |18446744073709551516              |
   > +----------------------------------+
   > ```
   > 
   > After this commit
   > 
   > ```
   > scala> sql("select conv(-100, 10, 10)").show(20, false)
   > +------------------+
   > |conv(-100, 10, 10)|
   > +------------------+
   > |-100              |
   > +------------------+
   > ```
   > 
   > If the `toBase` is positive, the result is unsigned. It's a bit hard to reason about how to put a negative value into an unsigned value, but MySQL returns the same result as before this commit and the overflow behavior seems to be desirable. @AngersZhuuuu can you take a look?
   
   Got it. 


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