diff --git a/pkg/common/event/dml_event.go b/pkg/common/event/dml_event.go
index bb0f19dcf3..a9b3443a63 100644
--- a/pkg/common/event/dml_event.go
+++ b/pkg/common/event/dml_event.go
@@ -344,7 +344,12 @@ func (b *BatchDMLEvent) GetStartTs() common.Ts {
 	return b.DMLEvents[0].GetStartTs()
 }
 
+// GetSize returns the in-memory size of the row payload.
+// Remote events keep their encoded rows in RawRows until AssembleRows decodes them.
 func (b *BatchDMLEvent) GetSize() int64 {
+	if b.Rows == nil {
+		return int64(len(b.RawRows))
+	}
 	return b.Rows.MemoryUsage()
 }
 
diff --git a/pkg/common/event/dml_event_test.go b/pkg/common/event/dml_event_test.go
index 7a04d9df42..8f4e499fed 100644
--- a/pkg/common/event/dml_event_test.go
+++ b/pkg/common/event/dml_event_test.go
@@ -216,6 +216,8 @@ func TestBatchDMLEventAssembleRowsKeepsOriginalTableInfoForLocalRowsWithoutRouti
 	require.Equal(t, "t", batchDMLEvent.TableInfo.GetTargetTableName())
 }
 
+// TestBatchDMLEventAssembleRowsDecodesRemoteRawRows verifies size accounting
+// before and after a remotely received batch decodes its raw row payload.
 func TestBatchDMLEventAssembleRowsDecodesRemoteRawRows(t *testing.T) {
 	helper := NewEventTestHelper(t)
 	defer helper.Close()
@@ -233,6 +235,9 @@ func TestBatchDMLEventAssembleRowsDecodesRemoteRawRows(t *testing.T) {
 		Rows:          dmlEvent.Rows,
 		TableInfo:     dmlEvent.TableInfo,
 	}
+	require.Equal(t, batchDMLEvent.Rows.MemoryUsage(), batchDMLEvent.GetSize())
+	require.Positive(t, batchDMLEvent.GetSize())
+
 	data, err := batchDMLEvent.Marshal()
 	require.NoError(t, err)
 
@@ -241,10 +246,13 @@ func TestBatchDMLEventAssembleRowsDecodesRemoteRawRows(t *testing.T) {
 	require.NoError(t, err)
 	require.Nil(t, reverseEvents.Rows)
 	require.NotEmpty(t, reverseEvents.RawRows)
+	require.Equal(t, int64(len(reverseEvents.RawRows)), reverseEvents.GetSize())
 
 	reverseEvents.AssembleRows(batchDMLEvent.TableInfo)
 
 	require.Nil(t, reverseEvents.RawRows)
+	require.Equal(t, reverseEvents.Rows.MemoryUsage(), reverseEvents.GetSize())
+	require.Positive(t, reverseEvents.GetSize())
 	require.Same(t, batchDMLEvent.TableInfo, reverseEvents.TableInfo)
 	require.Equal(t, batchDMLEvent.Rows.ToString(batchDMLEvent.TableInfo.GetFieldSlice()), reverseEvents.Rows.ToString(batchDMLEvent.TableInfo.GetFieldSlice()))
 }