Add method

clients/shared/append.go

@@ -21,7 +21,7 @@ func Append(dwh destination.DataWarehouse, tableData *optimization.TableData, op
 		return fmt.Errorf("failed to get table config: %w", err)
 	}
 
-	tableData.ReadOnlyInMemoryCols().DeleteColumn(constants.DeleteColumnMarker)
+	tableData.InMemoryColumns().DeleteColumn(constants.DeleteColumnMarker)
 
 	// We don't care about srcKeysMissing because we don't drop columns when we append.
 	_, targetKeysMissing := columns.Diff(

lib/optimization/table_data.go

@@ -74,6 +74,10 @@ func (t *TableData) Name() string {
 	return t.name
 }
 
+func (t *TableData) InMemoryColumns() *columns.Columns {
+	return t.inMemoryColumns
+}
+
 func (t *TableData) SetInMemoryColumns(columns *columns.Columns) {
 	t.inMemoryColumns = columns
 }