diff --git a/src/Analyzer/FunctionNode.cpp b/src/Analyzer/FunctionNode.cpp
index 36e4f1fc69b..323e6f02952 100644
--- a/src/Analyzer/FunctionNode.cpp
+++ b/src/Analyzer/FunctionNode.cpp
@@ -37,42 +37,27 @@ ColumnsWithTypeAndName FunctionNode::getArgumentTypes() const
     return argument_types;
 }
 
-
-FunctionBasePtr FunctionNode::getFunction() const
-{
-    return std::dynamic_pointer_cast<const IFunctionBase>(function);
-}
-
-AggregateFunctionPtr FunctionNode::getAggregateFunction() const
-{
-    return std::dynamic_pointer_cast<const IAggregateFunction>(function);
-}
-
-bool FunctionNode::isAggregateFunction() const
-{
-    return typeid_cast<AggregateFunctionPtr>(function) != nullptr && !isWindowFunction();
-}
-
-bool FunctionNode::isOrdinaryFunction() const
-{
-    return typeid_cast<FunctionBasePtr>(function) != nullptr;
-}
-
 void FunctionNode::resolveAsFunction(FunctionBasePtr function_value)
 {
     function_name = function_value->getName();
     function = std::move(function_value);
+    kind = FunctionKind::ORDINARY;
 }
 
 void FunctionNode::resolveAsAggregateFunction(AggregateFunctionPtr aggregate_function_value)
 {
     function_name = aggregate_function_value->getName();
     function = std::move(aggregate_function_value);
+    kind = FunctionKind::AGGREGATE;
 }
 
 void FunctionNode::resolveAsWindowFunction(AggregateFunctionPtr window_function_value)
 {
+    if (!hasWindow())
+        throw Exception(ErrorCodes::LOGICAL_ERROR,
+            "Trying to resolve FunctionNode without window definition as a window function {}", window_function_value->getName());
     resolveAsAggregateFunction(window_function_value);
+    kind = FunctionKind::WINDOW;
 }
 
 void FunctionNode::dumpTreeImpl(WriteBuffer & buffer, FormatState & format_state, size_t indent) const
diff --git a/src/Analyzer/FunctionNode.h b/src/Analyzer/FunctionNode.h
index 3a8c5445375..feeecfdb146 100644
--- a/src/Analyzer/FunctionNode.h
+++ b/src/Analyzer/FunctionNode.h
@@ -41,6 +41,14 @@ using AggregateFunctionPtr = std::shared_ptr<const IAggregateFunction>;
 class FunctionNode;
 using FunctionNodePtr = std::shared_ptr<FunctionNode>;
 
+enum class FunctionKind
+{
+    UNKNOWN,
+    ORDINARY,
+    AGGREGATE,
+    WINDOW,
+};
+
 class FunctionNode final : public IQueryTreeNode
 {
 public:
@@ -133,13 +141,23 @@ public:
     /** Get non aggregate function.
       * If function is not resolved nullptr returned.
       */
-    FunctionBasePtr getFunction() const;
+    FunctionBasePtr getFunction() const
+    {
+        if (kind != FunctionKind::ORDINARY)
+            return {};
+        return std::reinterpret_pointer_cast<const IFunctionBase>(function);
+    }
 
     /** Get aggregate function.
       * If function is not resolved nullptr returned.
       * If function is resolved as non aggregate function nullptr returned.
       */
-    AggregateFunctionPtr getAggregateFunction() const;
+    AggregateFunctionPtr getAggregateFunction() const
+    {
+        if (kind == FunctionKind::UNKNOWN || kind == FunctionKind::ORDINARY)
+            return {};
+        return std::reinterpret_pointer_cast<const IAggregateFunction>(function);
+    }
 
     /// Is function node resolved
     bool isResolved() const
@@ -150,14 +168,20 @@ public:
     /// Is function node window function
     bool isWindowFunction() const
     {
-        return getWindowNode() != nullptr;
+        return kind == FunctionKind::WINDOW;
     }
 
     /// Is function node aggregate function
-    bool isAggregateFunction() const;
+    bool isAggregateFunction() const
+    {
+        return kind == FunctionKind::AGGREGATE;
+    }
 
     /// Is function node ordinary function
-    bool isOrdinaryFunction() const;
+    bool isOrdinaryFunction() const
+    {
+        return kind == FunctionKind::ORDINARY;
+    }
 
     /** Resolve function node as non aggregate function.
       * It is important that function name is updated with resolved function name.
@@ -202,6 +226,7 @@ protected:
 
 private:
     String function_name;
+    FunctionKind kind = FunctionKind::UNKNOWN;
     IResolvedFunctionPtr function;
 
     static constexpr size_t parameters_child_index = 0;