diff --git a/internal/core/src/mmap/ChunkedColumn.h b/internal/core/src/mmap/ChunkedColumn.h
index 93d43bafa6b17..082d8e10e1aa1 100644
--- a/internal/core/src/mmap/ChunkedColumn.h
+++ b/internal/core/src/mmap/ChunkedColumn.h
@@ -157,15 +157,18 @@ class ChunkedColumnBase : public ColumnBase {
 
     std::pair<size_t, size_t>
     GetChunkIDByOffset(int64_t offset) const {
-        int chunk_id = 0;
-        for (auto& chunk : chunks_) {
-            if (offset < chunk->RowNums()) {
-                break;
-            }
-            offset -= chunk->RowNums();
-            chunk_id++;
-        }
-        return {chunk_id, offset};
+        AssertInfo(offset < num_rows_,
+                   "offset {} is out of range, num_rows: {}",
+                   offset,
+                   num_rows_);
+
+        auto iter = std::lower_bound(num_rows_until_chunk_.begin(),
+                                     num_rows_until_chunk_.end(),
+                                     offset + 1);
+        size_t chunk_idx =
+            std::distance(num_rows_until_chunk_.begin(), iter) - 1;
+        size_t offset_in_chunk = offset - num_rows_until_chunk_[chunk_idx];
+        return {chunk_idx, offset_in_chunk};
     }
 
     int64_t
diff --git a/internal/core/unittest/CMakeLists.txt b/internal/core/unittest/CMakeLists.txt
index 67d97b83c3fff..56123c7ef06e6 100644
--- a/internal/core/unittest/CMakeLists.txt
+++ b/internal/core/unittest/CMakeLists.txt
@@ -86,6 +86,7 @@ set(MILVUS_TEST_FILES
         test_tracer.cpp
         test_utils.cpp
         test_chunked_segment.cpp
+        test_chunked_column.cpp
         )
 
 if ( INDEX_ENGINE STREQUAL "cardinal" )
diff --git a/internal/core/unittest/test_chunked_column.cpp b/internal/core/unittest/test_chunked_column.cpp
new file mode 100644
index 0000000000000..e17de1163fe28
--- /dev/null
+++ b/internal/core/unittest/test_chunked_column.cpp
@@ -0,0 +1,36 @@
+// Copyright (C) 2019-2020 Zilliz. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance
+// with the License. You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software distributed under the License
+// is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
+// or implied. See the License for the specific language governing permissions and limitations under the License
+
+#include "common/Chunk.h"
+#include "gtest/gtest.h"
+#include "mmap/ChunkedColumn.h"
+namespace milvus {
+TEST(test_chunked_column, test_get_chunkid) {
+    ChunkedColumn column;
+    std::vector<size_t> chunk_row_nums = {10, 20, 30};
+    for (auto row_num : chunk_row_nums) {
+        auto chunk =
+            std::make_shared<FixedWidthChunk>(row_num, 1, nullptr, 0, 4, false);
+        column.AddChunk(chunk);
+    }
+
+    int offset = 0;
+    for (int i = 0; i < chunk_row_nums.size(); ++i) {
+        for (int j = 0; j < chunk_row_nums[i]; ++j) {
+            auto [chunk_id, offset_in_chunk] =
+                column.GetChunkIDByOffset(offset);
+            ASSERT_EQ(chunk_id, i);
+            ASSERT_EQ(offset_in_chunk, j);
+            offset++;
+        }
+    }
+}
+}  // namespace milvus
\ No newline at end of file