**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

{
    
    std::unique_lock lock(clear_old_temporary_directories_mutex, std::defer_lock);
    if (!lock.try_lock())
        return;
    const auto settings = getSettings();
    time_t current_time = time(nullptr);
    ssize_t deadline = (custom_directories_lifetime_seconds >= 0)
        ? current_time - custom_directories_lifetime_seconds
        : current_time - settings->temporary_directories_lifetime.totalSeconds();
    
    for (const auto & [path, disk] : getRelativeDataPathsWithDisks())
    {
        for (auto it = disk->iterateDirectory(path); it->isValid(); it->next())
        {
            if (startsWith(it->name(), "tmp_"))
            {
                try
                {
                    if (disk->isDirectory(it->path()) && isOldPartDirectory(disk, it->path(), deadline))
                    {
                        LOG_WARNING(log, "Removing temporary directory {}", fullPath(disk, it->path()));
                        disk->removeRecursive(it->path());
                    }
                }
                catch (const Poco::FileNotFoundException &)
                {
                    
                }
            }