**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_ERROR(log, "Detaching broken part {}{} because it covers less than 2 parts. You need to resolve this manually", getFullPathOnDisk(part_disk_ptr), part_name);
                        std::lock_guard loading_lock(mutex);
                        broken_parts_to_detach.push_back(part);
                        ++suspicious_broken_parts;
                    }
                }
                return;
            }
            if (!part->index_granularity_info.is_adaptive)
                has_non_adaptive_parts.store(true, std::memory_order_relaxed);
            else
                has_adaptive_parts.store(true, std::memory_order_relaxed);
            part->modification_time = part_disk_ptr->getLastModified(relative_data_path + part_name).epochTime();
            
            part->setState(DataPartState::Committed);
            std::lock_guard loading_lock(mutex);
            if (!data_parts_indexes.insert(part).second)
                throw Exception("Part " + part->name + " already exists", ErrorCodes::DUPLICATE_DATA_PART);
            addPartContributionToDataVolume(part);
        });
    }
    pool.wait();
    for (auto & part : parts_from_wal)
    {
        if (getActiveContainingPart(part->info, DataPartState::Committed, part_lock))
            continue;
        part->modification_time = time(nullptr);
        
        part->setState(DataPartState::Committed);
        if (!data_parts_indexes.insert(part).second)