rdblue commented on issue #24768: [SPARK-27919][SQL] Add v2 session catalog
URL: https://github.com/apache/spark/pull/24768#issuecomment-505228767
 
 
   The new v2 catalog is an alternative catalog API that Spark calls directly 
from physical plan nodes. Create, for example, calls a catalog to create a 
table. There is no proxy in the design and I don't think it makes sense to add 
one.
   
   The v2 catalogs change the way catalogs are used by Spark so that there is 
no singleton catalog used for all operations. Right now, the session catalog is 
used for table operations via `ExternalCatalog` as well as other purposes, like 
tracking temporary views. I think that is the source of confusion.
   
   A v2 catalog will not be responsible for tracking temporary views. But, that 
doesn't mean that v2 catalogs should be called through a singleton 
`SessionCatalog` that will track temporary views and proxy to catalogs. We 
should continue using the `SessionCatalog` for temporary views right now, and 
eventually separate out that functionality to an internal class to handle it, 
with a resolution rule for lookups.
   
   Does that make sense?

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