[GitHub] [spark] cloud-fan edited a comment on pull request #31541: Revert "[SPARK-34209][SQL] Delegate table name validation to the session catalog"

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

cloud-fan edited a comment on pull request #31541:
URL: https://github.com/apache/spark/pull/31541#issuecomment-780319947


   Technically people can replace the session catalog with a custom v2 implementation by setting `spark.sql.catalog.spark_catalog`, but this is not the expected usage:
   ```
     val V2_SESSION_CATALOG_IMPLEMENTATION =
       buildConf(s"spark.sql.catalog.$SESSION_CATALOG_NAME")
         .doc("A catalog implementation that will be used as the v2 interface to Spark's built-in " +
           s"v1 catalog: $SESSION_CATALOG_NAME. This catalog shares its identifier namespace with " +
           s"the $SESSION_CATALOG_NAME and must be consistent with it; for example, if a table can " +
           s"be loaded by the $SESSION_CATALOG_NAME, this catalog must also return the table " +
           s"metadata. To delegate operations to the $SESSION_CATALOG_NAME, implementations can " +
           "extend 'CatalogExtension'.")
         .version("3.0.0")
         .stringConf
         .createOptional
   ```
   
   Users are only expected to extend the session catalog, not replacing it. By "extend", I mean "This catalog shares its identifier namespace with the $SESSION_CATALOG_NAME and must be consistent with it". I believe that's what [Delta](https://docs.delta.io/latest/quick-start.html) does.


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