diff --git a/core/src/main/scala/org/apache/spark/resource/ResourceUtils.scala b/core/src/main/scala/org/apache/spark/resource/ResourceUtils.scala
index 36ef906439451..162f090f011c6 100644
--- a/core/src/main/scala/org/apache/spark/resource/ResourceUtils.scala
+++ b/core/src/main/scala/org/apache/spark/resource/ResourceUtils.scala
@@ -150,7 +150,7 @@ private[spark] object ResourceUtils extends Logging {
   def listResourceIds(sparkConf: SparkConf, componentName: String): Seq[ResourceID] = {
     sparkConf.getAllWithPrefix(s"$componentName.$RESOURCE_PREFIX.").map { case (key, _) =>
       key.substring(0, key.indexOf('.'))
-    }.toSet.toSeq.map(name => new ResourceID(componentName, name))
+    }.distinct.map(name => new ResourceID(componentName, name))
   }
 
   def parseAllResourceRequests(
diff --git a/core/src/main/scala/org/apache/spark/scheduler/ResultTask.scala b/core/src/main/scala/org/apache/spark/scheduler/ResultTask.scala
index 857c89d7a98f5..15f2161fac39d 100644
--- a/core/src/main/scala/org/apache/spark/scheduler/ResultTask.scala
+++ b/core/src/main/scala/org/apache/spark/scheduler/ResultTask.scala
@@ -69,7 +69,7 @@ private[spark] class ResultTask[T, U](
   with Serializable {
 
   @transient private[this] val preferredLocs: Seq[TaskLocation] = {
-    if (locs == null) Nil else locs.toSet.toSeq
+    if (locs == null) Nil else locs.distinct
   }
 
   override def runTask(context: TaskContext): U = {
diff --git a/core/src/main/scala/org/apache/spark/scheduler/ShuffleMapTask.scala b/core/src/main/scala/org/apache/spark/scheduler/ShuffleMapTask.scala
index 4c0c30a3caf67..a0ba9208ea647 100644
--- a/core/src/main/scala/org/apache/spark/scheduler/ShuffleMapTask.scala
+++ b/core/src/main/scala/org/apache/spark/scheduler/ShuffleMapTask.scala
@@ -71,7 +71,7 @@ private[spark] class ShuffleMapTask(
   }
 
   @transient private val preferredLocs: Seq[TaskLocation] = {
-    if (locs == null) Nil else locs.toSet.toSeq
+    if (locs == null) Nil else locs.distinct
   }
 
   override def runTask(context: TaskContext): MapStatus = {
diff --git a/core/src/main/scala/org/apache/spark/scheduler/TaskSchedulerImpl.scala b/core/src/main/scala/org/apache/spark/scheduler/TaskSchedulerImpl.scala
index 7e2fbb43e3098..f0f84fe63d1cf 100644
--- a/core/src/main/scala/org/apache/spark/scheduler/TaskSchedulerImpl.scala
+++ b/core/src/main/scala/org/apache/spark/scheduler/TaskSchedulerImpl.scala
@@ -487,7 +487,7 @@ private[spark] class TaskSchedulerImpl(
         newExecAvail = true
       }
     }
-    val hosts = offers.map(_.host).toSet.toSeq
+    val hosts = offers.map(_.host).distinct
     for ((host, Some(rack)) <- hosts.zip(getRacksForHosts(hosts))) {
       hostsByRack.getOrElseUpdate(rack, new HashSet[String]()) += host
     }
diff --git a/core/src/test/scala/org/apache/spark/scheduler/TaskSchedulerImplSuite.scala b/core/src/test/scala/org/apache/spark/scheduler/TaskSchedulerImplSuite.scala
index 9ee84a8179c77..b9a11e7f66c64 100644
--- a/core/src/test/scala/org/apache/spark/scheduler/TaskSchedulerImplSuite.scala
+++ b/core/src/test/scala/org/apache/spark/scheduler/TaskSchedulerImplSuite.scala
@@ -761,7 +761,7 @@ class TaskSchedulerImplSuite extends SparkFunSuite with LocalSparkContext with B
         // that are explicitly blacklisted, plus those that have *any* executors blacklisted.
         val nodesForBlacklistedExecutors = offers.filter { offer =>
           execBlacklist.contains(offer.executorId)
-        }.map(_.host).toSet.toSeq
+        }.map(_.host).distinct
         val nodesWithAnyBlacklisting = (nodeBlacklist ++ nodesForBlacklistedExecutors).toSet
         // Similarly, figure out which executors have any blacklisting.  This means all executors
         // that are explicitly blacklisted, plus all executors on nodes that are blacklisted.
diff --git a/sql/core/src/main/scala/org/apache/spark/sql/Dataset.scala b/sql/core/src/main/scala/org/apache/spark/sql/Dataset.scala
index e3c63881b07ac..e1e3e8e6722ef 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/Dataset.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/Dataset.scala
@@ -2455,7 +2455,7 @@ class Dataset[T] private[sql](
   def dropDuplicates(colNames: Seq[String]): Dataset[T] = withTypedPlan {
     val resolver = sparkSession.sessionState.analyzer.resolver
     val allColumns = queryExecution.analyzed.output
-    val groupCols = colNames.toSet.toSeq.flatMap { (colName: String) =>
+    val groupCols = colNames.distinct.flatMap { (colName: String) =>
       // It is possibly there are more than one columns with the same name,
       // so we call filter instead of find.
       val cols = allColumns.filter(col => resolver(col.name, colName))