[SPARK-5833] [SQL] Adds REFRESH TABLE command

Lifts `HiveMetastoreCatalog.refreshTable` to `Catalog`. Adds `RefreshTable` command to refresh (possibly cached) metadata in external data sources tables.

<!-- Reviewable:start -->
[<img src="https://reviewable.io/review_button.png" height=40 alt="Review on Reviewable"/>](https://reviewable.io/reviews/apache/spark/4624)
<!-- Reviewable:end -->

Author: Cheng Lian <lian@databricks.com>

Closes #4624 from liancheng/refresh-table and squashes the following commits:

8d1aa4c [Cheng Lian] Adds REFRESH TABLE command

1 files changed, 10 insertions, 0 deletions

diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/Catalog.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/Catalog.scala
index bf97215ee6..9e6e2912e0 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/Catalog.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/Catalog.scala
@@ -46,6 +46,8 @@ trait Catalog {
    */
   def getTables(databaseName: Option[String]): Seq[(String, Boolean)]
 
+  def refreshTable(databaseName: String, tableName: String): Unit
+
   def registerTable(tableIdentifier: Seq[String], plan: LogicalPlan): Unit
 
   def unregisterTable(tableIdentifier: Seq[String]): Unit
@@ -119,6 +121,10 @@ class SimpleCatalog(val caseSensitive: Boolean) extends Catalog {
       case (name, _) => (name, true)
     }.toSeq
   }
+
+  override def refreshTable(databaseName: String, tableName: String): Unit = {
+    throw new UnsupportedOperationException
+  }
 }
 
 /**
@@ -224,4 +230,8 @@ object EmptyCatalog extends Catalog {
   }
 
   override def unregisterAllTables(): Unit = {}
+
+  override def refreshTable(databaseName: String, tableName: String): Unit = {
+    throw new UnsupportedOperationException
+  }
 }