2010YOUY01 commented on issue #23461:
URL: https://github.com/apache/datafusion/issues/23461#issuecomment-5082515443

   Should we keep the error behavior, but provide a better error message? 🤔 
   
   From the Arrow spec, after joining two tables with conflicting metadata key, 
what's the expected behavior is unspecified, so I tend to think we should be 
more conservative.
   
   https://arrow.apache.org/docs/format/Columnar.html#schema-message
   
   After the fix in 
[https://github.com/apache/datafusion/pull/23605](https://github.com/apache/datafusion/pull/23605),
 the behavior becomes deterministic: when a metadata key conflicts, the value 
from the original right child of `CrossJoinExec` is used.
   
   Silently allowing one side to override the other is fairly confusing. It 
could propagate inconsistent metadata and trigger another bug later.
   
   However if certain application prefer such overriding behavior, we could 
specify it first (somewhere in arrow schema metadata spec), and then continue 
the fix.
   


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