Address comments.

python/pyspark/sql/context.py

@@ -624,7 +624,7 @@ def table(self, tableName):
     def tables(self, dbName=None):
         """Returns a DataFrame containing names of table in the given database.
 
-        If `dbName` is `None`, the database will be the current database.
+        If `dbName` is not specified, the current database will be used.
 
         The returned DataFrame has two columns, tableName and isTemporary
         (a column with BooleanType indicating if a table is a temporary one or not).

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/Catalog.scala

@@ -35,10 +35,10 @@ trait Catalog {
       alias: Option[String] = None): LogicalPlan
 
   /**
-   * Returns names and flags indicating if a table is temporary or not of all tables in the
-   * database identified by `databaseIdentifier`.
+   * Returns tuples of (tableName, isTemporary) for all tables in the given database.
+   * isTemporary is a Boolean value indicates if a table is a temporary or not.
    */
-  def getTables(databaseIdentifier: Seq[String]): Seq[(String, Boolean)]
+  def getTables(databaseName: Option[String]): Seq[(String, Boolean)]
 
   def registerTable(tableIdentifier: Seq[String], plan: LogicalPlan): Unit
 
@@ -66,10 +66,6 @@ trait Catalog {
   protected def getDBTable(tableIdent: Seq[String]) : (Option[String], String) = {
     (tableIdent.lift(tableIdent.size - 2), tableIdent.last)
   }
-
-  protected def getDBName(databaseIdentifier: Seq[String]): Option[String] = {
-    databaseIdentifier.lift(databaseIdentifier.size - 1)
-  }
 }
 
 class SimpleCatalog(val caseSensitive: Boolean) extends Catalog {
@@ -112,7 +108,7 @@ class SimpleCatalog(val caseSensitive: Boolean) extends Catalog {
     alias.map(a => Subquery(a, tableWithQualifiers)).getOrElse(tableWithQualifiers)
   }
 
-  override def getTables(databaseIdentifier: Seq[String]): Seq[(String, Boolean)] = {
+  override def getTables(databaseName: Option[String]): Seq[(String, Boolean)] = {
     tables.map {
       case (name, _) => (name, true)
     }.toSeq
@@ -153,20 +149,19 @@ trait OverrideCatalog extends Catalog {
     withAlias.getOrElse(super.lookupRelation(tableIdentifier, alias))
   }
 
-  abstract override def getTables(databaseIdentifier: Seq[String]): Seq[(String, Boolean)] = {
-    val dbName = getDBName(databaseIdentifier)
+  abstract override def getTables(databaseName: Option[String]): Seq[(String, Boolean)] = {
     val temporaryTables = overrides.filter {
       // If a temporary table does not have an associated database, we should return its name.
       case ((None, _), _) => true
       // If a temporary table does have an associated database, we should return it if the database
       // matches the given database name.
-      case ((db: Some[String], _), _) if db == dbName => true
+      case ((db: Some[String], _), _) if db == databaseName => true
       case _ => false
     }.map {
       case ((_, tableName), _) => (tableName, true)
     }.toSeq
 
-    temporaryTables ++ super.getTables(databaseIdentifier)
+    temporaryTables ++ super.getTables(databaseName)
   }
 
   override def registerTable(
@@ -204,7 +199,7 @@ object EmptyCatalog extends Catalog {
     throw new UnsupportedOperationException
   }
 
-  override def getTables(databaseIdentifier: Seq[String]): Seq[(String, Boolean)] = {
+  override def getTables(databaseName: Option[String]): Seq[(String, Boolean)] = {
     throw new UnsupportedOperationException
   }
 

sql/core/src/main/scala/org/apache/spark/sql/SQLContext.scala

@@ -740,7 +740,7 @@ class SQLContext(@transient val sparkContext: SparkContext)
    * indicating if a table is a temporary one or not).
    */
   def tables(databaseName: String): DataFrame = {
-    createDataFrame(catalog.getTables(Seq(databaseName))).toDataFrame("tableName", "isTemporary")
+    createDataFrame(catalog.getTables(Some(databaseName))).toDataFrame("tableName", "isTemporary")
   }
 
   /**
@@ -749,7 +749,7 @@ class SQLContext(@transient val sparkContext: SparkContext)
    * indicating if a table is a temporary one or not).
    */
   def tables(): DataFrame = {
-    createDataFrame(catalog.getTables(Seq.empty[String])).toDataFrame("tableName", "isTemporary")
+    createDataFrame(catalog.getTables(None)).toDataFrame("tableName", "isTemporary")
   }
 
   protected[sql] class SparkPlanner extends SparkStrategies {

sql/core/src/test/scala/org/apache/spark/sql/ListTablesSuite.scala

@@ -35,14 +35,14 @@ class ListTablesSuite extends QueryTest with BeforeAndAfterAll {
   }
 
   override def afterAll(): Unit = {
-    catalog.unregisterAllTables()
+    (1 to 10).foreach(i => catalog.unregisterTable(Seq(s"table$i")))
   }
 
-  test("get All Tables") {
+  test("get all tables") {
     checkAnswer(tables(), (1 to 10).map(i => Row(s"table$i", true)))
   }
 
-  test("getting All Tables with a database name has not impact on returned table names") {
+  test("getting all Tables with a database name has no impact on returned table names") {
     checkAnswer(tables("DB"), (1 to 10).map(i => Row(s"table$i", true)))
   }
 

sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveMetastoreCatalog.scala

@@ -198,8 +198,8 @@ private[hive] class HiveMetastoreCatalog(hive: HiveContext) extends Catalog with
     }
   }
 
-  override def getTables(databaseIdentifier: Seq[String]): Seq[(String, Boolean)] = {
-    val dbName = getDBName(databaseIdentifier).getOrElse(hive.sessionState.getCurrentDatabase)
+  override def getTables(databaseName: Option[String]): Seq[(String, Boolean)] = {
+    val dbName = databaseName.getOrElse(hive.sessionState.getCurrentDatabase)
     client.getAllTables(dbName).map(tableName => (tableName, false))
   }
 

sql/hive/src/test/scala/org/apache/spark/sql/hive/ListTablesSuite.scala

@@ -47,7 +47,8 @@ class ListTablesSuite extends QueryTest with BeforeAndAfterAll {
   }
 
   override def afterAll(): Unit = {
-    catalog.unregisterAllTables()
+    (1 to 10).foreach(i => catalog.unregisterTable(Seq(s"Table$i")))
+    (1 to 10).foreach(i => catalog.unregisterTable(Seq("db1", s"db1TempTable$i")))
     (1 to 10).foreach {
       i => sql(s"DROP TABLE IF EXISTS hivetable$i")
     }
@@ -57,15 +58,15 @@ class ListTablesSuite extends QueryTest with BeforeAndAfterAll {
     sql("DROP DATABASE IF EXISTS db1")
   }
 
-  test("get All Tables of current database") {
+  test("get all tables of current database") {
     // We are using default DB.
     val expectedTables =
       (1 to 10).map(i => Row(s"table$i", true)) ++
       (1 to 10).map(i => Row(s"hivetable$i", false))
     checkAnswer(tables(), expectedTables)
   }
 
-  test("getting All Tables with a database name has not impact on returned table names") {
+  test("getting all tables with a database name") {
     val expectedTables =
       // We are expecting to see Table1 to Table10 since there is no database associated with them.
       (1 to 10).map(i => Row(s"table$i", true)) ++