[SPARK-5195][sql]Update HiveMetastoreCatalog.scala(override the MetastoreRelation's sameresult method only compare databasename and table name)

override  the MetastoreRelation's  sameresult method only compare databasename and table name

because in previous :
cache table t1;
select count(*) from t1;
it will read data from memory  but the sql below will not,instead it read from hdfs:
select count(*) from t1 t;

because cache data is keyed by logical plan and compare with sameResult ,so  when table with alias  the same table 's logicalplan is not the same logical plan with out alias  so modify  the sameresult method only compare databasename and table name

Author: seayi <405078363@qq.com>
Author: Michael Armbrust <michael@databricks.com>

Closes #3898 from seayi/branch-1.2 and squashes the following commits:

8f0c7d2 [seayi] Update CachedTableSuite.scala
a277120 [seayi] Update HiveMetastoreCatalog.scala
8d910aa [seayi] Update HiveMetastoreCatalog.scala

2 files changed, 15 insertions, 0 deletions

diff --git a/sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveMetastoreCatalog.scala b/sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveMetastoreCatalog.scala
index bbf6752a56..1f562accd9 100644
--- a/sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveMetastoreCatalog.scala
+++ b/sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveMetastoreCatalog.scala
@@ -522,6 +522,15 @@ private[hive] case class MetastoreRelation
     }
   )
 
+  /** Only compare database and tablename, not alias. */
+  override def sameResult(plan: LogicalPlan): Boolean = {
+    plan match {
+      case mr: MetastoreRelation =>
+        mr.databaseName == databaseName && mr.tableName == tableName
+      case _ => false
+    }
+  }
+
   val tableDesc = HiveShim.getTableDesc(
     Class.forName(
       hiveQlTable.getSerializationLib,
diff --git a/sql/hive/src/test/scala/org/apache/spark/sql/hive/CachedTableSuite.scala b/sql/hive/src/test/scala/org/apache/spark/sql/hive/CachedTableSuite.scala
index f95a6b43af..1ff04e9d86 100644
--- a/sql/hive/src/test/scala/org/apache/spark/sql/hive/CachedTableSuite.scala
+++ b/sql/hive/src/test/scala/org/apache/spark/sql/hive/CachedTableSuite.scala
@@ -64,6 +64,12 @@ class CachedTableSuite extends QueryTest {
       sql("SELECT * FROM src"),
       preCacheResults)
 
+    assertCached(sql("SELECT * FROM src s"))
+
+    checkAnswer(
+      sql("SELECT * FROM src s"),
+      preCacheResults)
+    
     uncacheTable("src")
     assertCached(sql("SELECT * FROM src"), 0)
   }