[SPARK-19598][SQL] Remove the alias parameter in UnresolvedRelation

## What changes were proposed in this pull request?

Remove the alias parameter in `UnresolvedRelation`, and use `SubqueryAlias` to replace it.
This can simplify some `match case` situations.

For example, the broadcast hint pull request can have one fewer case https://github.com/apache/spark/blob/master/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/ResolveHints.scala#L57-L61

## How was this patch tested?
add some unit tests

Author: windpiger <songjun@outlook.com>

Closes #16956 from windpiger/removeUnresolveTableAlias.

3 files changed, 5 insertions, 6 deletions

diff --git a/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/rules.scala b/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/rules.scala
index 1c3e7c6d52..e7a59d4ad4 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/rules.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/rules.scala
@@ -52,8 +52,7 @@ class ResolveSQLOnFile(sparkSession: SparkSession) extends Rule[LogicalPlan] {
           throw new AnalysisException("Unsupported data source type for direct query on files: " +
             s"${u.tableIdentifier.database.get}")
         }
-        val plan = LogicalRelation(dataSource.resolveRelation())
-        u.alias.map(a => SubqueryAlias(a, plan, None)).getOrElse(plan)
+        LogicalRelation(dataSource.resolveRelation())
       } catch {
         case _: ClassNotFoundException => u
         case e: Exception =>
diff --git a/sql/core/src/test/scala/org/apache/spark/sql/JoinSuite.scala b/sql/core/src/test/scala/org/apache/spark/sql/JoinSuite.scala
index f780fc0ec0..2e006735d1 100644
--- a/sql/core/src/test/scala/org/apache/spark/sql/JoinSuite.scala
+++ b/sql/core/src/test/scala/org/apache/spark/sql/JoinSuite.scala
@@ -364,8 +364,8 @@ class JoinSuite extends QueryTest with SharedSQLContext {
     upperCaseData.where('N <= 4).createOrReplaceTempView("`left`")
     upperCaseData.where('N >= 3).createOrReplaceTempView("`right`")
 
-    val left = UnresolvedRelation(TableIdentifier("left"), None)
-    val right = UnresolvedRelation(TableIdentifier("right"), None)
+    val left = UnresolvedRelation(TableIdentifier("left"))
+    val right = UnresolvedRelation(TableIdentifier("right"))
 
     checkAnswer(
       left.join(right, $"left.N" === $"right.N", "full"),
diff --git a/sql/core/src/test/scala/org/apache/spark/sql/execution/benchmark/TPCDSQueryBenchmark.scala b/sql/core/src/test/scala/org/apache/spark/sql/execution/benchmark/TPCDSQueryBenchmark.scala
index 3988d9750b..239822b720 100644
--- a/sql/core/src/test/scala/org/apache/spark/sql/execution/benchmark/TPCDSQueryBenchmark.scala
+++ b/sql/core/src/test/scala/org/apache/spark/sql/execution/benchmark/TPCDSQueryBenchmark.scala
@@ -73,13 +73,13 @@ object TPCDSQueryBenchmark {
       // per-row processing time for those cases.
       val queryRelations = scala.collection.mutable.HashSet[String]()
       spark.sql(queryString).queryExecution.logical.map {
-        case ur @ UnresolvedRelation(t: TableIdentifier, _) =>
+        case ur @ UnresolvedRelation(t: TableIdentifier) =>
           queryRelations.add(t.table)
         case lp: LogicalPlan =>
           lp.expressions.foreach { _ foreach {
             case subquery: SubqueryExpression =>
               subquery.plan.foreach {
-                case ur @ UnresolvedRelation(t: TableIdentifier, _) =>
+                case ur @ UnresolvedRelation(t: TableIdentifier) =>
                   queryRelations.add(t.table)
                 case _ =>
               }