**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

{
    auto lock = lockParts();
    for (auto original_active_part : getDataPartsStateRange(DataPartState::Committed)) 
    {
        if (part_copy->name == original_active_part->name)
        {
            auto active_part_it = data_parts_by_info.find(original_active_part->info);
            if (active_part_it == data_parts_by_info.end())
                throw Exception("Cannot swap part '" + part_copy->name + "', no such active part.", ErrorCodes::NO_SUCH_DATA_PART);
            modifyPartState(original_active_part, DataPartState::DeleteOnDestroy);
            data_parts_indexes.erase(active_part_it);
            auto part_it = data_parts_indexes.insert(part_copy).first;
            modifyPartState(part_it, DataPartState::Committed);
            removePartContributionToDataVolume(original_active_part);
            addPartContributionToDataVolume(part_copy);
            auto disk = original_active_part->volume->getDisk();
            String marker_path = original_active_part->getFullRelativePath() + IMergeTreeDataPart::DELETE_ON_DESTROY_MARKER_FILE_NAME;
            try
            {