diff --git a/fe/fe-core/src/main/java/org/apache/doris/nereids/rules/expression/rules/RangeInference.java b/fe/fe-core/src/main/java/org/apache/doris/nereids/rules/expression/rules/RangeInference.java
index d8d9faa5371d6ff..74099df1123f25a 100644
--- a/fe/fe-core/src/main/java/org/apache/doris/nereids/rules/expression/rules/RangeInference.java
+++ b/fe/fe-core/src/main/java/org/apache/doris/nereids/rules/expression/rules/RangeInference.java
@@ -49,6 +49,9 @@
 import java.util.function.BinaryOperator;
 import java.util.stream.Collectors;
 
+/**
+ * collect range of expression
+ */
 public class RangeInference extends ExpressionVisitor<RangeInference.ValueDesc, ExpressionRewriteContext> {
 
     /*
@@ -156,7 +159,10 @@ private ValueDesc simplify(ExpressionRewriteContext context,
         return new UnknownValue(context, originExpr, valuePerRefs, isAnd);
     }
 
-    public static abstract class ValueDesc {
+    /**
+     * value desc
+     */
+    public abstract static class ValueDesc {
         ExpressionRewriteContext context;
         Expression toExpr;
         Expression reference;
@@ -181,6 +187,7 @@ public ExpressionRewriteContext getExpressionRewriteContext() {
 
         public abstract ValueDesc union(ValueDesc other);
 
+        /** or */
         public static ValueDesc union(ExpressionRewriteContext context,
                 RangeValue range, DiscreteValue discrete, boolean reverseOrder) {
             long count = discrete.values.stream().filter(x -> range.range.test(x)).count();
@@ -195,8 +202,10 @@ public static ValueDesc union(ExpressionRewriteContext context,
             return new UnknownValue(context, toExpr, sourceValues, false);
         }
 
+        /** intersect */
         public abstract ValueDesc intersect(ValueDesc other);
 
+        /** intersect */
         public static ValueDesc intersect(ExpressionRewriteContext context, RangeValue range, DiscreteValue discrete) {
             DiscreteValue result = new DiscreteValue(context, discrete.reference, discrete.toExpr);
             discrete.values.stream().filter(x -> range.range.contains(x)).forEach(result.values::add);
@@ -207,7 +216,7 @@ public static ValueDesc intersect(ExpressionRewriteContext context, RangeValue r
             return new EmptyValue(context, range.reference, originExpr);
         }
 
-        public static ValueDesc range(ExpressionRewriteContext context, ComparisonPredicate predicate) {
+        private static ValueDesc range(ExpressionRewriteContext context, ComparisonPredicate predicate) {
             Literal value = (Literal) predicate.right();
             if (predicate instanceof EqualTo) {
                 return new DiscreteValue(context, predicate.left(), predicate, value);
@@ -233,6 +242,9 @@ public static ValueDesc discrete(ExpressionRewriteContext context, InPredicate i
         }
     }
 
+    /**
+     * empty range
+     */
     public static class EmptyValue extends ValueDesc {
 
         public EmptyValue(ExpressionRewriteContext context, Expression reference, Expression toExpr) {
diff --git a/fe/fe-core/src/main/java/org/apache/doris/nereids/rules/expression/rules/SimplifyRange.java b/fe/fe-core/src/main/java/org/apache/doris/nereids/rules/expression/rules/SimplifyRange.java
index 8934e57fed76f58..628d94d1dccafde 100644
--- a/fe/fe-core/src/main/java/org/apache/doris/nereids/rules/expression/rules/SimplifyRange.java
+++ b/fe/fe-core/src/main/java/org/apache/doris/nereids/rules/expression/rules/SimplifyRange.java
@@ -162,7 +162,6 @@ private Expression getExpression(DiscreteValue value) {
     }
 
     private Expression getExpression(UnknownValue value) {
-        Expression reference = value.getReference();
         List<ValueDesc> sourceValues = value.getSourceValues();
         Expression originExpr = value.getOriginExpr();
         if (sourceValues.isEmpty()) {