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.
}
    
    
    auto result_part = MergeTreePartInfo::fromPartName(new_part_name, format_version);
    
    for (const auto & future_part_elem : future_parts)
    {
        auto future_part = MergeTreePartInfo::fromPartName(future_part_elem.first, format_version);
        if (future_part.contains(result_part))
        {
            const char * format_str = "Not executing log entry {} for part {} "
                                      "because it is covered by part {} that is currently executing.";
            LOG_TRACE(log, format_str, log_entry_name, new_part_name, future_part_elem.first);
            out_reason = fmt::format(format_str, log_entry_name, new_part_name, future_part_elem.first);
            return false;
        }
    }
    return true;
}
bool ReplicatedMergeTreeQueue::addFuturePartIfNotCoveredByThem(const String & part_name, LogEntry & entry, String & reject_reason)
{
    std::lock_guard lock(state_mutex);
    if (isNotCoveredByFuturePartsImpl(entry.znode_name, part_name, reject_reason, lock))
    {
        CurrentlyExecuting::setActualPartName(entry, part_name, *this);
        return true;
    }
    return false;
}
bool ReplicatedMergeTreeQueue::shouldExecuteLogEntry(