for (int item = 0, itemCount = this.rows.size(); item < itemCount; 
                 item++) {
                row = (KeyedObjects) this.rows.get(item);
                int colIndex = row.getIndex(columnKey);
                if (colIndex >= 0) {
                    row.removeValue(colIndex);
                }
            }
            this.columnKeys.remove(columnKey);