**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

{
    DataPartsVector res;
    {
        auto lock = lockParts();
        res.assign(data_parts_by_info.begin(), data_parts_by_info.end());
        if (out_states != nullptr)
        {
            out_states->resize(res.size());
            for (size_t i = 0; i < res.size(); ++i)
                (*out_states)[i] = res[i]->getState();
        }
    }
    return res;
}
std::vector<DetachedPartInfo>