diff --git a/internal/core/src/mmap/ChunkVector.h b/internal/core/src/mmap/ChunkVector.h
index 3e155fd172306..7b024a603f93b 100644
--- a/internal/core/src/mmap/ChunkVector.h
+++ b/internal/core/src/mmap/ChunkVector.h
@@ -43,6 +43,9 @@ class ChunkVectorBase {
     virtual SpanBase
     get_span(int64_t chunk_id) = 0;
 
+    virtual bool
+    is_mmap() const = 0;
+
  protected:
     std::atomic<int64_t> counter_ = 0;
 };
@@ -103,7 +106,7 @@ class ThreadSafeChunkVector : public ChunkVectorBase<Type> {
     ChunkViewType<Type>
     view_element(int64_t chunk_id, int64_t chunk_offset) override {
         std::shared_lock<std::shared_mutex> lck(mutex_);
-        auto chunk = vec_[chunk_id];
+        auto& chunk = vec_[chunk_id];
         if constexpr (IsMmap) {
             return chunk.view(chunk_offset);
         } else if constexpr (std::is_same_v<std::string, Type>) {
@@ -161,6 +164,11 @@ class ThreadSafeChunkVector : public ChunkVectorBase<Type> {
         }
     }
 
+    bool
+    is_mmap() const override {
+        return mmap_descriptor_ != nullptr;
+    }
+
  private:
     mutable std::shared_mutex mutex_;
     storage::MmapChunkDescriptorPtr mmap_descriptor_ = nullptr;
diff --git a/internal/core/src/query/GroupByOperator.h b/internal/core/src/query/GroupByOperator.h
index 4ef1297bf1df5..4c8f94622a361 100644
--- a/internal/core/src/query/GroupByOperator.h
+++ b/internal/core/src/query/GroupByOperator.h
@@ -51,10 +51,12 @@ class GrowingDataGetter : public DataGetter<T> {
     T
     Get(int64_t idx) const {
         if constexpr (std::is_same_v<std::string, T>) {
-            return T(growing_raw_data_->view_element(idx));
-        } else {
-            return growing_raw_data_->operator[](idx);
+            if (growing_raw_data_->is_mmap()) {
+                // when scalar data is mapped, it's needed to get the scalar data view and reconstruct string from the view
+                return T(growing_raw_data_->view_element(idx));
+            }
         }
+        return growing_raw_data_->operator[](idx);
     }
 };
 
diff --git a/internal/core/src/segcore/ConcurrentVector.h b/internal/core/src/segcore/ConcurrentVector.h
index 3591758d0292a..01e76843a3825 100644
--- a/internal/core/src/segcore/ConcurrentVector.h
+++ b/internal/core/src/segcore/ConcurrentVector.h
@@ -290,6 +290,11 @@ class ConcurrentVectorImpl : public VectorBase {
         chunks_ptr_->clear();
     }
 
+    bool
+    is_mmap() const {
+        return chunks_ptr_->is_mmap();
+    }
+
  private:
     void
     set_data(ssize_t element_offset,