**Describe the bug**

I have a table like:

```
CREATE TABLE test (
    time DateTime64(3)
    ...
) ENGINE = MergeTree()
PARTITION BY toStartOfInterval(time, INTERVAL 1 HOUR)
...
```

But when I search in `system.parts` it does not appear to have the `min/max` columns appropriately set?

```
partition:                             2020-06-01 01:00:00
min_date:                              1970-01-01
max_date:                              1970-01-01
min_time:                              1970-01-01 00:00:00
max_time:                              1970-01-01 00:00:00
```

I assume that if these were correctly set, doing a `select toStartOfInterval(time, interval 1 day), count()` type query would be pretty instant rather than trying to scan everything? I am guessing this is due to the `DateTime64` type in use?

Clickhouse 20.11.3.3

{
    MutationCommands commands = getFirstAlterMutationCommandsForPart(part);
    AlterConversions result{};
    for (const auto & command : commands)
        
        
        
        if (command.type == MutationCommand::Type::RENAME_COLUMN)
            result.rename_map[command.rename_to] = command.column_name;
    return result;
}
MergeTreeData::WriteAheadLogPtr MergeTreeData::getWriteAheadLog()
{
    std::lock_guard lock(write_ahead_log_mutex);
    if (!write_ahead_log)
    {
        auto reservation = reserveSpace(getSettings()->write_ahead_log_max_bytes);
        write_ahead_log = std::make_shared<MergeTreeWriteAheadLog>(*this, reservation->getDisk());
    }
    return write_ahead_log;
}
NamesAndTypesList MergeTreeData::getVirtuals() const