Execute:

```
alter table tbl enable feature "UPDATE_FLEXIBLE_COLUMNS";
```

The generated SQL in binlog:

```
ALTER TABLE `t` ADD COLUMN `__DORIS_SKIP_BITMAP_COL__` bitmap NONE NOT NULL DEFAULT BITMAP_EMPTY COMMENT "doris skip bitmap hidden column" AFTER `__DORIS_VERSION_COL__` 
```

The error message:

```
Error 1105 (HY000): errCode = 2, detailMessage = mismatched input 'NONE' expecting {<EOF>, ';'}(line 1, pos 62)
```