HaoYang670 commented on issue #4615:
URL: 
https://github.com/apache/arrow-datafusion/issues/4615#issuecomment-1362378488

   > Well I think the rationale / question is if SQL expression semantics allow 
/ require eager evaluation or if delayed evaluation
   
   These are the variants for runtime behavior, not related to compile time 
checking I think.
   I've done some tests on Postgres, and find the expression `when FALSE then 
...` will be removed before type checking, so if you have the expr `when FALSE 
then 1/0` in your query, it is always valid: 
https://onecompiler.com/postgresql/3yskvh35x
   
   But if the invalid expression can not be removed at compile time, a `Divide 
by zero` error will always return before executing the query, even if the 
invalid code won't be touched at runtime: 
https://onecompiler.com/postgresql/3yskvqaxf


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