[SPARK-14177][SQL] Native Parsing for DDL Command "Describe Database" and "Alter Database"

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

This PR is to provide native parsing support for two DDL commands:  ```Describe Database``` and ```Alter Database Set Properties```

Based on the Hive DDL document:
https://cwiki.apache.org/confluence/display/Hive/LanguageManual+DDL

##### 1. ALTER DATABASE
**Syntax:**
```SQL
ALTER (DATABASE|SCHEMA) database_name SET DBPROPERTIES (property_name=property_value, ...)
```
 - `ALTER DATABASE` is to add new (key, value) pairs into `DBPROPERTIES`

##### 2. DESCRIBE DATABASE
**Syntax:**
```SQL
DESCRIBE DATABASE [EXTENDED] db_name
```
 - `DESCRIBE DATABASE` shows the name of the database, its comment (if one has been set), and its root location on the filesystem. When `extended` is true, it also shows the database's properties

#### How was this patch tested?
Added the related test cases to `DDLCommandSuite`

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

This patch had conflicts when merged, resolved by
Committer: Yin Huai <yhuai@databricks.com>

Closes #11977 from gatorsmile/parseAlterDatabase.

1 files changed, 38 insertions, 0 deletions

diff --git a/sql/core/src/test/scala/org/apache/spark/sql/execution/command/DDLCommandSuite.scala b/sql/core/src/test/scala/org/apache/spark/sql/execution/command/DDLCommandSuite.scala
index 18f48ffa94..7a6343748b 100644
--- a/sql/core/src/test/scala/org/apache/spark/sql/execution/command/DDLCommandSuite.scala
+++ b/sql/core/src/test/scala/org/apache/spark/sql/execution/command/DDLCommandSuite.scala
@@ -101,6 +101,44 @@ class DDLCommandSuite extends PlanTest {
     comparePlans(parsed7, expected7)
   }
 
+  test("alter database set dbproperties") {
+    // ALTER (DATABASE|SCHEMA) database_name SET DBPROPERTIES (property_name=property_value, ...)
+    val sql1 = "ALTER DATABASE database_name SET DBPROPERTIES ('a'='a', 'b'='b', 'c'='c')"
+    val sql2 = "ALTER SCHEMA database_name SET DBPROPERTIES ('a'='a')"
+
+    val parsed1 = parser.parsePlan(sql1)
+    val parsed2 = parser.parsePlan(sql2)
+
+    val expected1 = AlterDatabaseProperties(
+      "database_name",
+      Map("a" -> "a", "b" -> "b", "c" -> "c"))(sql1)
+    val expected2 = AlterDatabaseProperties(
+      "database_name",
+      Map("a" -> "a"))(sql2)
+
+    comparePlans(parsed1, expected1)
+    comparePlans(parsed2, expected2)
+  }
+
+  test("describe database") {
+    // DESCRIBE DATABASE [EXTENDED] db_name;
+    val sql1 = "DESCRIBE DATABASE EXTENDED db_name"
+    val sql2 = "DESCRIBE DATABASE db_name"
+
+    val parsed1 = parser.parsePlan(sql1)
+    val parsed2 = parser.parsePlan(sql2)
+
+    val expected1 = DescribeDatabase(
+      "db_name",
+      extended = true)(sql1)
+    val expected2 = DescribeDatabase(
+      "db_name",
+      extended = false)(sql2)
+
+    comparePlans(parsed1, expected1)
+    comparePlans(parsed2, expected2)
+  }
+
   test("create function") {
     val sql1 =
       """