**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

for (const auto & part : covered_parts)
                submerging_big_parts_from_partition.insert(part->name);
            for (const auto & part : getDataPartsStateRange(MergeTreeData::DataPartState::Committed))
            {
                if (part->isStoredOnDisk() && part->getBytesOnDisk() >= min_bytes_to_rebalance_partition_over_jbod
                    && part_info.partition_id == part->info.partition_id)
                {
                    auto name = part->volume->getDisk()->getName();
                    auto it = disk_occupation.find(name);
                    if (it != disk_occupation.end())
                    {
                        if (submerging_big_parts_from_partition.find(part->name) == submerging_big_parts_from_partition.end())
                        {
                            it->second += part->getBytesOnDisk();
                            disk_parts_for_logging[name].push_back(formatReadableSizeWithBinarySuffix(part->getBytesOnDisk()));
                            committed_big_parts_from_partition.insert(part->name);
                        }
                        else
                        {
                            disk_parts_for_logging[name].push_back(formatReadableSizeWithBinarySuffix(part->getBytesOnDisk()) + " (submerging)");
                        }
                    }
                    else
                    {
                        
                    }
                }
            }
        }
        for (const auto & [name, emerging_part] : currently_emerging_big_parts)