[GitHub] [spark] cloud-fan commented on pull request #31553: [WIP][SPARK-34425][SQL] Clarify error message

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

cloud-fan commented on pull request #31553:
URL: https://github.com/apache/spark/pull/31553#issuecomment-780368362


   As I mentioned in https://github.com/apache/spark/pull/31541#issuecomment-780319947 , people can extend the session catalog by a custom v2 catalog, but it must share the same table/view/function namespace with the session catalog.
   
   That said, the original check does make sense. When we look up a table/view/function from the extended session catalog and eventually forward the request to the underlying Hive catalog, we should make sure the identifier is 2-parts.
   
   Looking at https://github.com/apache/spark/pull/31427 , it seems like your motivation is to extend the session catalog by using additional table/view/function namespaces. Then the original check doesn't make sense anymore as the session catalog can support arbitrary levels of namespaces. I don't have a problem with it, as long as it still follows the config doc: `if a table can be loaded by the $SESSION_CATALOG_NAME, this catalog must also return the table metadata`.
   
   Following this direction, my remaining concerns are:
   1. we should have a test case for the extended session catalog that supports more than 2 name parts in identifiers.
   2. we should unify the error message. For views/functions that have more than 2 name parts, we should throw view/function not found exception as well, not `Unsupported function name: xxx`


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