**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

{
    LOG_DEBUG(log, "Loading data parts");
    auto metadata_snapshot = getInMemoryMetadataPtr();
    const auto settings = getSettings();
    std::vector<std::pair<String, DiskPtr>> part_names_with_disks;
    MutableDataPartsVector parts_from_wal;
    Strings part_file_names;
    auto disks = getStoragePolicy()->getDisks();
    
    if (!getStoragePolicy()->isDefaultPolicy() && !skip_sanity_checks)
    {
        
        std::unordered_set<String> defined_disk_names;
        for (const auto & disk_ptr : disks)
            defined_disk_names.insert(disk_ptr->getName());
        for (const auto & [disk_name, disk] : global_context.getDisksMap())
        {
            if (defined_disk_names.count(disk_name) == 0 && disk->exists(relative_data_path))
            {
                for (const auto it = disk->iterateDirectory(relative_data_path); it->isValid(); it->next())
                {
                    MergeTreePartInfo part_info;
                    if (MergeTreePartInfo::tryParsePartName(it->name(), &part_info, format_version))
                        throw Exception("Part " + backQuote(it->name()) + " was found on disk " + backQuote(disk_name) + " which is not defined in the storage policy", ErrorCodes::UNKNOWN_DISK);
                }
            }
        }
    }