diff --git a/be/src/vec/olap/vgeneric_iterators.cpp b/be/src/vec/olap/vgeneric_iterators.cpp
index 94792cb69dfebc..0a7b2124204dea 100644
--- a/be/src/vec/olap/vgeneric_iterators.cpp
+++ b/be/src/vec/olap/vgeneric_iterators.cpp
@@ -178,9 +178,7 @@ class VMergeIteratorContext {
         vectorized::Block& src = _block;
         vectorized::Block& dst = *block;
 
-        auto columns = _iter->schema().columns();
-
-        for (size_t i = 0; i < columns.size(); ++i) {
+        for (size_t i = 0; i < _iter->schema().num_column_ids(); ++i) {
             vectorized::ColumnWithTypeAndName s_col = src.get_by_position(i);
             vectorized::ColumnWithTypeAndName d_col = dst.get_by_position(i);