[GitHub] [spark] cloud-fan commented on a change in pull request #30079: [SPARK-33174][SQL] Migrate DROP TABLE to use UnresolvedTableOrView to resolve the identifier

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cloud-fan commented on a change in pull request #30079:
URL: https://github.com/apache/spark/pull/30079#discussion_r509947710



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File path: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/v2ResolutionPlans.scala
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@@ -45,12 +45,25 @@ case class UnresolvedTable(multipartIdentifier: Seq[String]) extends LeafNode {
 /**
  * Holds the name of a table or view that has yet to be looked up in a catalog. It will
  * be resolved to [[ResolvedTable]] or [[ResolvedView]] during analysis.
+ *
+ * If 'isResolutionRequired' is set to false and the name cannot be resolved to a table or view,
+ * [[UnresolvedTableOrView]] will be converted to [[NotFoundTableOrView]].
  */
-case class UnresolvedTableOrView(multipartIdentifier: Seq[String]) extends LeafNode {
+case class UnresolvedTableOrView(
+    multipartIdentifier: Seq[String],
+    isResolutionRequired: Boolean = true) extends LeafNode {
   override lazy val resolved: Boolean = false
   override def output: Seq[Attribute] = Nil
 }
 
+/**
+ * Holds the name of a table or view that has been looked up in a catalog, but not found.
+ * This is a "resolved" logical.
+ */
+case class NotFoundTableOrView(multipartIdentifier: Seq[String]) extends LeafNode {

Review comment:
       If this is specific to DROP TABLE, let's avoid changing the framework. How about we add a rule in the `Post-Hoc Resolution` batch in the analyzer:
   ```
   object ResolveNoopDropTable extends Rule[LogicalPlan] {
     def apply(plan: LogicalPlan) = plan.transform {
        case DropTable(_: UnresolvedTableOrView, _, true) => NoopDropTable
     }
   }
   ```
   where `NoopDropTable` is a new command that does nothing but only keeping the table name for EXPLAIN.




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