address comments.

Author: gatorsmile

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

@@ -17,6 +17,8 @@
 
 package org.apache.spark.sql.catalyst.analysis
 
+import java.util.Locale
+
 import org.apache.spark.sql.catalyst.expressions.Expression
 import org.apache.spark.sql.catalyst.plans.logical.{LogicalPlan, Range}
 import org.apache.spark.sql.catalyst.rules._
@@ -103,7 +105,7 @@ object ResolveTableValuedFunctions extends Rule[LogicalPlan] {
 
   override def apply(plan: LogicalPlan): LogicalPlan = plan resolveOperators {
     case u: UnresolvedTableValuedFunction if u.functionArgs.forall(_.resolved) =>
-      builtinFunctions.get(u.functionName.toLowerCase()) match {
+      builtinFunctions.get(u.functionName.toLowerCase(Locale.ROOT)) match {
         case Some(tvf) =>
           val resolved = tvf.flatMap { case (argList, resolver) =>
             argList.implicitCast(u.functionArgs) match {

sql/core/src/main/scala/org/apache/spark/sql/internal/SharedState.scala

@@ -17,6 +17,8 @@
 
 package org.apache.spark.sql.internal
 
+import java.util.Locale
+
 import scala.reflect.ClassTag
 import scala.util.control.NonFatal
 
@@ -114,7 +116,7 @@ private[sql] class SharedState(val sparkContext: SparkContext) extends Logging {
     // System preserved database should not exists in metastore. However it's hard to guarantee it
     // for every session, because case-sensitivity differs. Here we always lowercase it to make our
     // life easier.
-    val globalTempDB = sparkContext.conf.get(GLOBAL_TEMP_DATABASE).toLowerCase
+    val globalTempDB = sparkContext.conf.get(GLOBAL_TEMP_DATABASE).toLowerCase(Locale.ROOT)
     if (externalCatalog.databaseExists(globalTempDB)) {
       throw new SparkException(
         s"$globalTempDB is a system preserved database, please rename your existing database " +