**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

std::map<String, std::vector<String>> disk_parts_for_logging;
        for (const auto & disk : disks)
            disk_occupation.emplace(disk->getName(), 0);
        std::set<String> committed_big_parts_from_partition;
        std::set<String> submerging_big_parts_from_partition;
        std::lock_guard lock(currently_submerging_emerging_mutex);
        for (const auto & part : currently_submerging_big_parts)
        {
            if (part_info.partition_id == part->info.partition_id)
                submerging_big_parts_from_partition.insert(part->name);
        }
        {
            auto lock_parts = lockParts();
            if (covered_parts.empty())
            {
                
                MergeTreeData::DataPartPtr covering_part;
                covered_parts = getActivePartsToReplace(part_info, part_name, covering_part, lock_parts);
            }
            
            covered_parts.erase(
                std::remove_if(
                    covered_parts.begin(),
                    covered_parts.end(),
                    [min_bytes_to_rebalance_partition_over_jbod](const auto & part)
                    {
                        return !(part->isStoredOnDisk() && part->getBytesOnDisk() >= min_bytes_to_rebalance_partition_over_jbod);
                    }),
                covered_parts.end());