Change to String type as comment suggested

Author: jerryshao

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/catalog/ExternalCatalog.scala

@@ -157,9 +157,9 @@ abstract class ExternalCatalog
   final def alterTable(tableDefinition: CatalogTable): Unit = {
     val db = tableDefinition.database
     val name = tableDefinition.identifier.table
-    postToAll(AlterTablePreEvent(db, name, AlterTableKind.Table))
+    postToAll(AlterTablePreEvent(db, name, AlterTableKind.TABLE))
     doAlterTable(tableDefinition)
-    postToAll(AlterTableEvent(db, name, AlterTableKind.Table))
+    postToAll(AlterTableEvent(db, name, AlterTableKind.TABLE))
   }
 
   protected def doAlterTable(tableDefinition: CatalogTable): Unit
@@ -174,18 +174,18 @@ abstract class ExternalCatalog
    * @param newDataSchema Updated data schema to be used for the table.
    */
   final def alterTableDataSchema(db: String, table: String, newDataSchema: StructType): Unit = {
-    postToAll(AlterTablePreEvent(db, table, AlterTableKind.DataSchema))
+    postToAll(AlterTablePreEvent(db, table, AlterTableKind.DATASCHEMA))
     doAlterTableDataSchema(db, table, newDataSchema)
-    postToAll(AlterTableEvent(db, table, AlterTableKind.DataSchema))
+    postToAll(AlterTableEvent(db, table, AlterTableKind.DATASCHEMA))
   }
 
   protected def doAlterTableDataSchema(db: String, table: String, newDataSchema: StructType): Unit
 
   /** Alter the statistics of a table. If `stats` is None, then remove all existing statistics. */
   final def alterTableStats(db: String, table: String, stats: Option[CatalogStatistics]): Unit = {
-    postToAll(AlterTablePreEvent(db, table, AlterTableKind.Stats))
+    postToAll(AlterTablePreEvent(db, table, AlterTableKind.STATS))
     doAlterTableStats(db, table, stats)
-    postToAll(AlterTableEvent(db, table, AlterTableKind.Stats))
+    postToAll(AlterTableEvent(db, table, AlterTableKind.STATS))
   }
 
   protected def doAlterTableStats(db: String, table: String, stats: Option[CatalogStatistics]): Unit

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/catalog/events.scala

@@ -120,11 +120,13 @@ case class RenameTableEvent(
   extends TableEvent
 
 /**
- * Enumeration to indicate which part of table is altered. If a plain alterTable API is called, then
+ * String to indicate which part of table is altered. If a plain alterTable API is called, then
  * type will generally be Table.
  */
 object AlterTableKind extends Enumeration {
-  val Table, DataSchema, Stats = Value
+  val TABLE = "table"
+  val DATASCHEMA = "dataSchema"
+  val STATS = "stats"
 }
 
 /**
@@ -133,15 +135,15 @@ object AlterTableKind extends Enumeration {
 case class AlterTablePreEvent(
     database: String,
     name: String,
-    kind: AlterTableKind.Value) extends TableEvent
+    kind: String) extends TableEvent
 
 /**
  * Event fired after a table is altered.
  */
 case class AlterTableEvent(
     database: String,
     name: String,
-    kind: AlterTableKind.Value) extends TableEvent
+    kind: String) extends TableEvent
 
 /**
  * Event fired when a function is created, dropped, altered or renamed.

sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/catalog/ExternalCatalogEventSuite.scala

@@ -127,19 +127,19 @@ class ExternalCatalogEventSuite extends SparkFunSuite {
     // ALTER
     val newTableDefinition = tableDefinition.copy(tableType = CatalogTableType.EXTERNAL)
     catalog.alterTable(newTableDefinition)
-    checkEvents(AlterTablePreEvent("db5", "tbl1", AlterTableKind.Table) ::
-      AlterTableEvent("db5", "tbl1", AlterTableKind.Table) :: Nil)
+    checkEvents(AlterTablePreEvent("db5", "tbl1", AlterTableKind.TABLE) ::
+      AlterTableEvent("db5", "tbl1", AlterTableKind.TABLE) :: Nil)
 
     // ALTER schema
     val newSchema = new StructType().add("id", "long", nullable = false)
     catalog.alterTableDataSchema("db5", "tbl1", newSchema)
-    checkEvents(AlterTablePreEvent("db5", "tbl1", AlterTableKind.DataSchema) ::
-      AlterTableEvent("db5", "tbl1", AlterTableKind.DataSchema) :: Nil)
+    checkEvents(AlterTablePreEvent("db5", "tbl1", AlterTableKind.DATASCHEMA) ::
+      AlterTableEvent("db5", "tbl1", AlterTableKind.DATASCHEMA) :: Nil)
 
     // ALTER stats
     catalog.alterTableStats("db5", "tbl1", None)
-    checkEvents(AlterTablePreEvent("db5", "tbl1", AlterTableKind.Stats) ::
-      AlterTableEvent("db5", "tbl1", AlterTableKind.Stats) :: Nil)
+    checkEvents(AlterTablePreEvent("db5", "tbl1", AlterTableKind.STATS) ::
+      AlterTableEvent("db5", "tbl1", AlterTableKind.STATS) :: Nil)
 
     // RENAME
     catalog.renameTable("db5", "tbl1", "tbl2")