[WIP][SPARK-28476][SQL] Support ALTER DATABASE SET LOCATION

sql/catalyst/src/main/antlr4/org/apache/spark/sql/catalyst/parser/SqlBase.g4

@@ -89,6 +89,8 @@ statement
          (WITH DBPROPERTIES tablePropertyList))*                       #createDatabase
     | ALTER database db=errorCapturingIdentifier
         SET DBPROPERTIES tablePropertyList                             #setDatabaseProperties
+    | ALTER database db=errorCapturingIdentifier
+        SET locationSpec                                               #setDatabaseLocation
     | DROP database (IF EXISTS)? db=errorCapturingIdentifier
         (RESTRICT | CASCADE)?                                          #dropDatabase
     | SHOW DATABASES (LIKE? pattern=STRING)?                           #showDatabases

sql/core/src/main/scala/org/apache/spark/sql/execution/SparkSqlParser.scala

@@ -532,6 +532,22 @@ class SparkSqlAstBuilder(conf: SQLConf) extends AstBuilder(conf) {
       visitPropertyKeyValues(ctx.tablePropertyList))
   }
 
+  /**
+   * Create an [[AlterDatabaseLocationCommand]] command.
+   *
+   * For example:
+   * {{{
+   *   ALTER (DATABASE|SCHEMA) database SET LOCATION path;
+   * }}}
+   */
+  override def visitSetDatabaseLocation(
+    ctx: SetDatabaseLocationContext): LogicalPlan = withOrigin(ctx) {
+      AlterDatabaseLocationCommand(
+        ctx.db.getText,
+        visitLocationSpec(ctx.locationSpec())
+      )
+  }
+
   /**
    * Create a [[DropDatabaseCommand]] command.
    *

sql/core/src/main/scala/org/apache/spark/sql/execution/command/ddl.scala

@@ -132,6 +132,27 @@ case class AlterDatabasePropertiesCommand(
   }
 }
 
+/**
+ * A command for users to set new location path for a database
+ * If the database does not exist, an error message will be issued to indicate the database
+ * does not exist.
+ * The syntax of using this command in SQL is:
+ * {{{
+ *    ALTER (DATABASE|SCHEMA) database_name SET LOCATION path
+ * }}}
+ */
+case class AlterDatabaseLocationCommand(databaseName: String, location: String)
+  extends RunnableCommand {
+
+  override def run(sparkSession: SparkSession): Seq[Row] = {
+    val catalog = sparkSession.sessionState.catalog
+    val db: CatalogDatabase = catalog.getDatabaseMetadata(databaseName)
+    catalog.alterDatabase(db.copy(locationUri = CatalogUtils.stringToURI(location)))
+
+    Seq.empty[Row]
+  }
+}
+
 /**
  * A command for users to show 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

sql/core/src/test/scala/org/apache/spark/sql/execution/command/DDLParserSuite.scala

@@ -184,6 +184,15 @@ class DDLParserSuite extends AnalysisTest with SharedSQLContext {
       containsThesePhrases = Seq("key_without_value"))
   }
 
+  test("alter database set location") {
+    // ALTER (DATABASE|SCHEMA) database_name SET LOCATION
+    val sql1 = "ALTER DATABASE database_name SET LOCATION '/home/user/db'"
+    val parsed1 = parser.parsePlan(sql1)
+
+    val expected1 = AlterDatabaseLocationCommand("database_name", "/home/user/db")
+    comparePlans(parsed1, expected1)
+  }
+
   test("describe database") {
     // DESCRIBE DATABASE [EXTENDED] db_name;
     val sql1 = "DESCRIBE DATABASE EXTENDED db_name"