diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/util/QuantileSummaries.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/util/QuantileSummaries.scala
index 7512ace18856..e23123254ab9 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/util/QuantileSummaries.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/util/QuantileSummaries.scala
@@ -17,7 +17,7 @@
 
 package org.apache.spark.sql.catalyst.util
 
-import scala.collection.mutable.ArrayBuffer
+import scala.collection.mutable.{ArrayBuffer, ListBuffer}
 
 import org.apache.spark.sql.catalyst.util.QuantileSummaries.Stats
 
@@ -61,7 +61,12 @@ class QuantileSummaries(
   def insert(x: Double): QuantileSummaries = {
     headSampled += x
     if (headSampled.size >= defaultHeadSize) {
-      this.withHeadBufferInserted
+      val result = this.withHeadBufferInserted
+      if (result.sampled.length >= compressThreshold) {
+        result.compress()
+      } else {
+        result
+      }
     } else {
       this
     }
@@ -236,7 +241,7 @@ object QuantileSummaries {
     if (currentSamples.isEmpty) {
       return Array.empty[Stats]
     }
-    val res: ArrayBuffer[Stats] = ArrayBuffer.empty
+    val res = ListBuffer.empty[Stats]
     // Start for the last element, which is always part of the set.
     // The head contains the current new head, that may be merged with the current element.
     var head = currentSamples.last