diff --git a/paimon-common/src/main/java/org/apache/paimon/utils/HllSketchUtil.java b/paimon-common/src/main/java/org/apache/paimon/utils/HllSketchUtil.java
index 34c5464f7106..609862dafc20 100644
--- a/paimon-common/src/main/java/org/apache/paimon/utils/HllSketchUtil.java
+++ b/paimon-common/src/main/java/org/apache/paimon/utils/HllSketchUtil.java
@@ -21,10 +21,20 @@
 import org.apache.paimon.annotation.VisibleForTesting;
 
 import org.apache.datasketches.hll.HllSketch;
+import org.apache.datasketches.hll.TgtHllType;
+import org.apache.datasketches.hll.Union;
 
 /** A compressed bitmap for 32-bit integer. */
 public class HllSketchUtil {
 
+    public static byte[] union(byte[] sketchBytes1, byte[] sketchBytes2) {
+        HllSketch heapify = HllSketch.heapify((byte[]) sketchBytes1);
+        org.apache.datasketches.hll.Union union = Union.heapify((byte[]) sketchBytes2);
+        union.update(heapify);
+        HllSketch result = union.getResult(TgtHllType.HLL_4);
+        return result.toCompactByteArray();
+    }
+
     @VisibleForTesting
     public static byte[] sketchOf(int... values) {
         HllSketch hllSketch = new HllSketch();
diff --git a/paimon-core/src/main/java/org/apache/paimon/mergetree/compact/aggregate/FieldHllSketchAgg.java b/paimon-core/src/main/java/org/apache/paimon/mergetree/compact/aggregate/FieldHllSketchAgg.java
index 93901753645a..0ccf4af6497c 100644
--- a/paimon-core/src/main/java/org/apache/paimon/mergetree/compact/aggregate/FieldHllSketchAgg.java
+++ b/paimon-core/src/main/java/org/apache/paimon/mergetree/compact/aggregate/FieldHllSketchAgg.java
@@ -19,10 +19,7 @@
 package org.apache.paimon.mergetree.compact.aggregate;
 
 import org.apache.paimon.types.VarBinaryType;
-
-import org.apache.datasketches.hll.HllSketch;
-import org.apache.datasketches.hll.TgtHllType;
-import org.apache.datasketches.hll.Union;
+import org.apache.paimon.utils.HllSketchUtil;
 
 /** HllSketch aggregate a field of a row. */
 public class FieldHllSketchAgg extends FieldAggregator {
@@ -50,10 +47,6 @@ public Object agg(Object accumulator, Object inputField) {
             return accumulator == null ? inputField : accumulator;
         }
 
-        HllSketch heapify = HllSketch.heapify((byte[]) accumulator);
-        Union union = Union.heapify((byte[]) inputField);
-        union.update(heapify);
-        HllSketch result = union.getResult(TgtHllType.HLL_4);
-        return result.toCompactByteArray();
+        return HllSketchUtil.union((byte[]) accumulator, (byte[]) inputField);
     }
 }