[SPARK-14362][SPARK-14406][SQL] DDL Native Support: Drop View and Drop Table

#### What changes were proposed in this pull request?

This PR is to provide a native support for DDL `DROP VIEW` and `DROP TABLE`. The PR includes native parsing and native analysis.

Based on the HIVE DDL document for [DROP_VIEW_WEB_LINK](https://cwiki.apache.org/confluence/display/Hive/LanguageManual+DDL#LanguageManualDDL-
DropView
), `DROP VIEW` is defined as,
**Syntax:**
```SQL
DROP VIEW [IF EXISTS] [db_name.]view_name;
```
 - to remove metadata for the specified view.
 - illegal to use DROP TABLE on a view.
 - illegal to use DROP VIEW on a table.
 - this command only works in `HiveContext`. In `SQLContext`, we will get an exception.

This PR also handles `DROP TABLE`.
**Syntax:**
```SQL
DROP TABLE [IF EXISTS] table_name [PURGE];
```
- Previously, the `DROP TABLE` command only can drop Hive tables in `HiveContext`. Now, after this PR, this command also can drop temporary table, external table, external data source table in `SQLContext`.
- In `HiveContext`, we will not issue an exception if the to-be-dropped table does not exist and users did not specify `IF EXISTS`. Instead, we just log an error message. If `IF EXISTS` is specified, we will not issue any error message/exception.
- In `SQLContext`, we will issue an exception if the to-be-dropped table does not exist, unless `IF EXISTS` is specified.
- Data will not be deleted if the tables are `external`, unless table type is `managed_table`.

#### How was this patch tested?
For verifying command parsing, added test cases in `spark/sql/hive/HiveDDLCommandSuite.scala`
For verifying command analysis, added test cases in `spark/sql/hive/execution/HiveDDLSuite.scala`

Author: gatorsmile <gatorsmile@gmail.com>
Author: xiaoli <lixiao1983@gmail.com>
Author: Xiao Li <xiaoli@Xiaos-MacBook-Pro.local>

Closes #12146 from gatorsmile/dropView.

4 files changed, 6 insertions, 43 deletions

diff --git a/sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveExternalCatalog.scala b/sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveExternalCatalog.scala
index b1156fb3e2..a49ce33ba1 100644
--- a/sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveExternalCatalog.scala
+++ b/sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveExternalCatalog.scala
@@ -182,6 +182,10 @@ private[spark] class HiveExternalCatalog(client: HiveClient) extends ExternalCat
     client.getTable(db, table)
   }
 
+  override def getTableOption(db: String, table: String): Option[CatalogTable] = withClient {
+    client.getTableOption(db, table)
+  }
+
   override def tableExists(db: String, table: String): Boolean = withClient {
     client.getTableOption(db, table).isDefined
   }
diff --git a/sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveSessionCatalog.scala b/sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveSessionCatalog.scala
index 0cccc22e5a..875652c226 100644
--- a/sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveSessionCatalog.scala
+++ b/sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveSessionCatalog.scala
@@ -70,6 +70,8 @@ private[sql] class HiveSessionCatalog(
     }
   }
 
+  override def isViewSupported: Boolean = true
+
   // ----------------------------------------------------------------
   // | Methods and fields for interacting with HiveMetastoreCatalog |
   // ----------------------------------------------------------------
diff --git a/sql/hive/src/main/scala/org/apache/spark/sql/hive/execution/HiveSqlParser.scala b/sql/hive/src/main/scala/org/apache/spark/sql/hive/execution/HiveSqlParser.scala
index 657edb493a..7a435117e7 100644
--- a/sql/hive/src/main/scala/org/apache/spark/sql/hive/execution/HiveSqlParser.scala
+++ b/sql/hive/src/main/scala/org/apache/spark/sql/hive/execution/HiveSqlParser.scala
@@ -104,19 +104,6 @@ class HiveSqlAstBuilder extends SparkSqlAstBuilder {
   }
 
   /**
-   * Create a [[DropTable]] command.
-   */
-  override def visitDropTable(ctx: DropTableContext): LogicalPlan = withOrigin(ctx) {
-    if (ctx.PURGE != null) {
-      logWarning("PURGE option is ignored.")
-    }
-    if (ctx.REPLICATION != null) {
-      logWarning("REPLICATION clause is ignored.")
-    }
-    DropTable(visitTableIdentifier(ctx.tableIdentifier).toString, ctx.EXISTS != null)
-  }
-
-  /**
    * Create an [[AnalyzeTable]] command. This currently only implements the NOSCAN option (other
    * options are passed on to Hive) e.g.:
    * {{{
diff --git a/sql/hive/src/main/scala/org/apache/spark/sql/hive/execution/commands.scala b/sql/hive/src/main/scala/org/apache/spark/sql/hive/execution/commands.scala
index 64d1341a47..06badff474 100644
--- a/sql/hive/src/main/scala/org/apache/spark/sql/hive/execution/commands.scala
+++ b/sql/hive/src/main/scala/org/apache/spark/sql/hive/execution/commands.scala
@@ -46,36 +46,6 @@ case class AnalyzeTable(tableName: String) extends RunnableCommand {
   }
 }
 
-/**
- * Drops a table from the metastore and removes it if it is cached.
- */
-private[hive]
-case class DropTable(
-    tableName: String,
-    ifExists: Boolean) extends RunnableCommand {
-
-  override def run(sqlContext: SQLContext): Seq[Row] = {
-    val hiveContext = sqlContext.asInstanceOf[HiveContext]
-    val ifExistsClause = if (ifExists) "IF EXISTS " else ""
-    try {
-      hiveContext.cacheManager.tryUncacheQuery(hiveContext.table(tableName))
-    } catch {
-      // This table's metadata is not in Hive metastore (e.g. the table does not exist).
-      case _: org.apache.hadoop.hive.ql.metadata.InvalidTableException =>
-      case _: org.apache.spark.sql.catalyst.analysis.NoSuchTableException =>
-      // Other Throwables can be caused by users providing wrong parameters in OPTIONS
-      // (e.g. invalid paths). We catch it and log a warning message.
-      // Users should be able to drop such kinds of tables regardless if there is an error.
-      case e: Throwable => log.warn(s"${e.getMessage}", e)
-    }
-    hiveContext.invalidateTable(tableName)
-    hiveContext.runSqlHive(s"DROP TABLE $ifExistsClause$tableName")
-    hiveContext.sessionState.catalog.dropTable(
-      TableIdentifier(tableName), ignoreIfNotExists = true)
-    Seq.empty[Row]
-  }
-}
-
 private[hive]
 case class AddJar(path: String) extends RunnableCommand {