[SPARK-19028][SQL] Fixed non-thread-safe functions used in SessionCat…

…alog

### What changes were proposed in this pull request?
Fixed non-thread-safe functions used in SessionCatalog:
- refreshTable
- lookupRelation

### How was this patch tested?
N/A

Author: gatorsmile <gatorsmile@gmail.com>

Closes #16437 from gatorsmile/addSyncToLookUpTable.

(cherry picked from commit 35e9740)
Signed-off-by: Wenchen Fan <wenchen@databricks.com>

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/catalog/SessionCatalog.scala

@@ -632,7 +632,7 @@ class SessionCatalog(
   /**
    * Refresh the cache entry for a metastore table, if any.
    */
-  def refreshTable(name: TableIdentifier): Unit = {
+  def refreshTable(name: TableIdentifier): Unit = synchronized {
     // Go through temporary tables and invalidate them.
     // If the database is defined, this is definitely not a temp table.
     // If the database is not defined, there is a good chance this is a temp table.

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

@@ -56,23 +56,25 @@ private[sql] class HiveSessionCatalog(
     hadoopConf) {
 
   override def lookupRelation(name: TableIdentifier, alias: Option[String]): LogicalPlan = {
-    val table = formatTableName(name.table)
-    val db = formatDatabaseName(name.database.getOrElse(currentDb))
-    if (db == globalTempViewManager.database) {
-      val relationAlias = alias.getOrElse(table)
-      globalTempViewManager.get(table).map { viewDef =>
-        SubqueryAlias(relationAlias, viewDef, Some(name))
-      }.getOrElse(throw new NoSuchTableException(db, table))
-    } else if (name.database.isDefined || !tempTables.contains(table)) {
-      val database = name.database.map(formatDatabaseName)
-      val newName = name.copy(database = database, table = table)
-      metastoreCatalog.lookupRelation(newName, alias)
-    } else {
-      val relation = tempTables(table)
-      val tableWithQualifiers = SubqueryAlias(table, relation, None)
-      // If an alias was specified by the lookup, wrap the plan in a subquery so that
-      // attributes are properly qualified with this alias.
-      alias.map(a => SubqueryAlias(a, tableWithQualifiers, None)).getOrElse(tableWithQualifiers)
+    synchronized {
+      val table = formatTableName(name.table)
+      val db = formatDatabaseName(name.database.getOrElse(currentDb))
+      if (db == globalTempViewManager.database) {
+        val relationAlias = alias.getOrElse(table)
+        globalTempViewManager.get(table).map { viewDef =>
+          SubqueryAlias(relationAlias, viewDef, Some(name))
+        }.getOrElse(throw new NoSuchTableException(db, table))
+      } else if (name.database.isDefined || !tempTables.contains(table)) {
+        val database = name.database.map(formatDatabaseName)
+        val newName = name.copy(database = database, table = table)
+        metastoreCatalog.lookupRelation(newName, alias)
+      } else {
+        val relation = tempTables(table)
+        val tableWithQualifiers = SubqueryAlias(table, relation, None)
+        // If an alias was specified by the lookup, wrap the plan in a subquery so that
+        // attributes are properly qualified with this alias.
+        alias.map(a => SubqueryAlias(a, tableWithQualifiers, None)).getOrElse(tableWithQualifiers)
+      }
     }
   }