**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

MutableColumns & columns, std::vector<UInt8> & columns_mask, const StoragesInfo & info, bool has_state_column)
{
    using State = IMergeTreeDataPart::State;
    MergeTreeData::DataPartStateVector all_parts_state;
    MergeTreeData::DataPartsVector all_parts;
    all_parts = info.getParts(all_parts_state, has_state_column);
    for (size_t part_number = 0; part_number < all_parts.size(); ++part_number)
    {