Looks like https://github.com/ClickHouse/ClickHouse/pull/21303 is broke also "clear column" for such columns.

How to reproduce:

```
CREATE TABLE test.TTAdmLog
(
    `ts` DateTime,
    `event_date` Date DEFAULT toDate(ts),
    `impression_id` String DEFAULT '',
    `creative_id` String DEFAULT '',
    `creative_adm` String DEFAULT '',
    `impression_id_compressed` FixedString(16) DEFAULT UUIDStringToNum(impression_id),
    `impression_id_hashed` UInt16 DEFAULT reinterpretAsUInt16(impression_id_compressed),
)
ENGINE = ReplicatedMergeTree('/clickhouse/tables/{shard}/TTAdmLogTest', '{replica}')
PARTITION BY toMonday(event_date)
ORDER BY (event_date, impression_id_hashed)
SAMPLE BY impression_id_hashed
SETTINGS replicated_deduplication_window = 1000, replicated_deduplication_window_seconds = 864000, index_granularity = 8192

CREATE MATERIALIZED VIEW test.TTView
(
    `event_date` Date,
    `creative_id` String,
    `creative_adm` AggregateFunction(anyLast, String),
)
ENGINE = ReplicatedAggregatingMergeTree('/clickhouse/tables/{shard}/TTViewTest', '{replica}', event_date, (event_date, creative_id), 8192) AS
SELECT 
    toStartOfMonth(event_date) AS event_date,
    arrayJoin(splitByChar(',', creative_id)) AS creative_id,
    anyLastState(creative_adm) AS creative_adm,
FROM test.TTAdmLog
GROUP BY 
    event_date,
    creative_id,

```


ClickHouse server version 20.9.3 revision 54439.

```
alter table test.TTAdmLog clear column creative_adm in partition '2021-03-22'

OK

```
ClickHouse server version 21.4.3 revision 54447.

```
alter table test.TTAdmLog  clear column creative_adm in partition '2021-03-22'

DB::Exception: Trying to ALTER DROP column creative_adm which is referenced by materialized view ['TTView'].

```

* Otherwise there is race condition - merge of blocks could happen in interval that doesn't yet contain new part.
      */
    if (increment)
    {
        part_info.min_block = part_info.max_block = increment->get();
        part_info.mutation = 0; 
        part_name = part->getNewName(part_info);
    }
    else 
        part_name = part->name;
    LOG_TRACE(log, "Renaming temporary part {} to {}.", part->relative_path, part_name);
    auto it_duplicate = data_parts_by_info.find(part_info);
    if (it_duplicate != data_parts_by_info.end())
    {
        String message = "Part " + (*it_duplicate)->getNameWithState() + " already exists";
        if ((*it_duplicate)->checkState({DataPartState::Outdated, DataPartState::Deleting}))
            throw Exception(message + ", but it will be deleted soon", ErrorCodes::PART_IS_TEMPORARILY_LOCKED);
        throw Exception(message, ErrorCodes::DUPLICATE_DATA_PART);
    }
    DataPartPtr covering_part;
    DataPartsVector covered_parts = getActivePartsToReplace(part_info, part_name, covering_part, lock);
    DataPartsVector covered_parts_in_memory;
    if (covering_part)
    {
        LOG_WARNING(log, "Tried to add obsolete part {} covered by {}", part_name, covering_part->getNameWithState());
        return false;
    }