**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

{
    switch (type.getValue())
    {
        case MergeTreeDataPartType::WIDE:
            CurrentMetrics::sub(CurrentMetrics::PartsWide);
            return;
        case MergeTreeDataPartType::COMPACT:
            CurrentMetrics::sub(CurrentMetrics::PartsCompact);
            return;
        case MergeTreeDataPartType::IN_MEMORY:
            CurrentMetrics::sub(CurrentMetrics::PartsInMemory);
            return;
        case MergeTreeDataPartType::UNKNOWN:
            return;
    }
}
IMergeTreeDataPart::IMergeTreeDataPart(
    MergeTreeData & storage_, const String & name_, const VolumePtr & volume_, const std::optional<String> & relative_path_, Type part_type_)
    : storage(storage_)
    , name(name_)
    , info(MergeTreePartInfo::fromPartName(name_, storage.format_version))
    , volume(volume_)
    , relative_path(relative_path_.value_or(name_))
    , index_granularity_info(storage_, part_type_)
    , part_type(part_type_)
{
    incrementStateMetric(state);
    incrementTypeMetric(part_type);
}
IMergeTreeDataPart::IMergeTreeDataPart(