One of our users just killed mutations produced by `ALTER MODIFY` queries on 21 servers. After that new alters on three servers stuck with:
```
Cannot execute alter metadata with version: 8 because another alter 7 must be executed before
```

However, there is no corresponding alter №7 in the replication queue and no undone mutations:
```
select * from system.mutations where is_done = 0
```

However, in the ZooKeeper, we have the correct state of metadata_version:
```
Row 13:
───────
name:           metadata_version
value:          7
czxid:          23078663291
mzxid:          29401964979
ctime:          2020-09-02 17:52:08
mtime:          2020-11-13 00:43:18
version:        7
cversion:       0
aversion:       0
ephemeralOwner: 0
dataLength:     1
numChildren:    0
pzxid:          23078663291
```
`SYSTEM RESTART REPLICA dbname.table_name` solves the issue, but it seems like` KILL MUTATION` in some cases can lead to unfinished alter.
zkutil::ZooKeeperPtr zookeeper,
    std::optional<time_t> min_unprocessed_insert_time_changed,
    std::optional<time_t> max_processed_insert_time_changed) const
{
    
    
    
    Coordination::Requests ops;
    if (min_unprocessed_insert_time_changed)
        ops.emplace_back(zkutil::makeSetRequest(
            replica_path + "/min_unprocessed_insert_time", toString(*min_unprocessed_insert_time_changed), -1));
    if (max_processed_insert_time_changed)
        ops.emplace_back(zkutil::makeSetRequest(
            replica_path + "/max_processed_insert_time", toString(*max_processed_insert_time_changed), -1));
    if (!ops.empty())
    {
        Coordination::Responses responses;
        auto code = zookeeper->tryMulti(ops, responses);
        if (code != Coordination::Error::ZOK)
            LOG_ERROR(log, "Couldn't set value of nodes for insert times ({}/min_unprocessed_insert_time, max_processed_insert_time): {}. This shouldn't happen often.", replica_path, Coordination::errorMessage(code));
    }
}
void ReplicatedMergeTreeQueue::removeProcessedEntry(zkutil::ZooKeeperPtr zookeeper, LogEntryPtr & entry)