rdblue commented on issue #23836: [SPARK-26915][SQL] DataFrameWriter.save()  
should write without schema validation
URL: https://github.com/apache/spark/pull/23836#issuecomment-466100319
 
 
   > the current translation is not precise: append mode doesn't mean append, 
it's actually "create table if not exist or append table"
   
   Agreed. This is why we need to get CTAS finished.
   
   > The next problem is, how to implement "create table if not exist or append 
table" with ds v2 APIs.
   
   My understanding is that the plan is to do both. If a catalog supports 
staged tables, then Spark uses them to perform an atomic operation. If it 
doesn't, then Spark uses the create/append/drop-on-error strategy.
   
   I agree that option 2 is "better" in that the operation is atomic. But 
sources are not required to support atomic CTAS. We need both options, so they 
are not mutually exclusive.

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