**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

return;
    }
    
    size_t num_threads = std::min(size_t(settings->max_part_loading_threads), part_names_with_disks.size());
    std::mutex mutex;
    DataPartsVector broken_parts_to_remove;
    DataPartsVector broken_parts_to_detach;
    size_t suspicious_broken_parts = 0;
    std::atomic<bool> has_adaptive_parts = false;
    std::atomic<bool> has_non_adaptive_parts = false;
    ThreadPool pool(num_threads);
    for (size_t i = 0; i < part_names_with_disks.size(); ++i)
    {
        pool.scheduleOrThrowOnError([&, i]
        {
            const auto & part_name = part_names_with_disks[i].first;
            const auto part_disk_ptr = part_names_with_disks[i].second;
            MergeTreePartInfo part_info;
            if (!MergeTreePartInfo::tryParsePartName(part_name, &part_info, format_version))
                return;
            auto single_disk_volume = std::make_shared<SingleDiskVolume>("volume_" + part_name, part_disk_ptr, 0);
            auto part = createPart(part_name, part_info, single_disk_volume, part_name);
            bool broken = false;
            String part_path = relative_data_path + "/" + part_name;
            String marker_path = part_path + "/" + IMergeTreeDataPart::DELETE_ON_DESTROY_MARKER_FILE_NAME;
            if (part_disk_ptr->exists(marker_path))
            {
                LOG_WARNING(log, "Detaching stale part {}{}, which should have been deleted after a move. That can only happen after unclean restart of ClickHouse after move of a part having an operation blocking that stale copy of part.", getFullPathOnDisk(part_disk_ptr), part_name);
                std::lock_guard loading_lock(mutex);
                broken_parts_to_detach.push_back(part);