[SPARK-17680][SQL][TEST] Added a Testcase for Verifying Unicode Character...

[SPARK-17680][SQL][TEST] Added a Testcase for Verifying Unicode Character Support for Column Names and Comments

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

Spark SQL supports Unicode characters for column names when specified within backticks(`). When the Hive support is enabled, the version of the Hive metastore must be higher than 0.12,  See the JIRA: https://issues.apache.org/jira/browse/HIVE-6013 Hive metastore supports Unicode characters for column names since 0.13.

In Spark SQL, table comments, and view comments always allow Unicode characters without backticks.

BTW, a separate PR has been submitted for database and table name validation because we do not support Unicode characters in these two cases.
### How was this patch tested?

N/A

Author: gatorsmile <gatorsmile@gmail.com>

Closes #15255 from gatorsmile/unicodeSupport.

sql/hive/src/test/scala/org/apache/spark/sql/hive/execution/HiveDDLSuite.scala

@@ -147,6 +147,51 @@ class HiveDDLSuite
     }
   }
 
+  test("create Hive-serde table and view with unicode columns and comment") {
+    val catalog = spark.sessionState.catalog
+    val tabName = "tab1"
+    val viewName = "view1"
+    // scalastyle:off
+    // non ascii characters are not allowed in the source code, so we disable the scalastyle.
+    val colName1 = "和"
+    val colName2 = "尼"
+    val comment = "庙"
+    // scalastyle:on
+    withTable(tabName) {
+      sql(s"""
+             |CREATE TABLE $tabName(`$colName1` int COMMENT '$comment')
+             |COMMENT '$comment'
+             |PARTITIONED BY (`$colName2` int)
+           """.stripMargin)
+      sql(s"INSERT OVERWRITE TABLE $tabName partition (`$colName2`=2) SELECT 1")
+      withView(viewName) {
+        sql(
+          s"""
+             |CREATE VIEW $viewName(`$colName1` COMMENT '$comment', `$colName2`)
+             |COMMENT '$comment'
+             |AS SELECT `$colName1`, `$colName2` FROM $tabName
+           """.stripMargin)
+        val tableMetadata = catalog.getTableMetadata(TableIdentifier(tabName, Some("default")))
+        val viewMetadata = catalog.getTableMetadata(TableIdentifier(viewName, Some("default")))
+        assert(tableMetadata.comment == Option(comment))
+        assert(viewMetadata.comment == Option(comment))
+
+        assert(tableMetadata.schema.fields.length == 2 && viewMetadata.schema.fields.length == 2)
+        val column1InTable = tableMetadata.schema.fields.head
+        val column1InView = viewMetadata.schema.fields.head
+        assert(column1InTable.name == colName1 && column1InView.name == colName1)
+        assert(column1InTable.getComment() == Option(comment))
+        assert(column1InView.getComment() == Option(comment))
+
+        assert(tableMetadata.schema.fields(1).name == colName2 &&
+          viewMetadata.schema.fields(1).name == colName2)
+
+        checkAnswer(sql(s"SELECT `$colName1`, `$colName2` FROM $tabName"), Row(1, 2) :: Nil)
+        checkAnswer(sql(s"SELECT `$colName1`, `$colName2` FROM $viewName"), Row(1, 2) :: Nil)
+      }
+    }
+  }
+
   test("create table: partition column names exist in table definition") {
     val e = intercept[AnalysisException] {
       sql("CREATE TABLE tbl(a int) PARTITIONED BY (a string)")