**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

if (columns_mask[src_index++])
            columns[res_index++]->insert(static_cast<UInt64>(part->modification_time));
        if (columns_mask[src_index++])
        {
            time_t remove_time = part->remove_time.load(std::memory_order_relaxed);
            columns[res_index++]->insert(static_cast<UInt64>(remove_time == std::numeric_limits<time_t>::max() ? 0 : remove_time));
        }
        
        if (columns_mask[src_index++])
            columns[res_index++]->insert(static_cast<UInt64>(part.use_count() - 1));
        if (columns_mask[src_index++])
            columns[res_index++]->insert(part->getMinDate());
        if (columns_mask[src_index++])
            columns[res_index++]->insert(part->getMaxDate());
        if (columns_mask[src_index++])
            columns[res_index++]->insert(static_cast<UInt32>(part->getMinTime()));
        if (columns_mask[src_index++])
            columns[res_index++]->insert(static_cast<UInt32>(part->getMaxTime()));
        if (columns_mask[src_index++])
            columns[res_index++]->insert(part->info.partition_id);
        if (columns_mask[src_index++])
            columns[res_index++]->insert(part->info.min_block);
        if (columns_mask[src_index++])
            columns[res_index++]->insert(part->info.max_block);
        if (columns_mask[src_index++])
            columns[res_index++]->insert(part->info.level);
        if (columns_mask[src_index++])
            columns[res_index++]->insert(static_cast<UInt64>(part->info.getDataVersion()));
        if (columns_mask[src_index++])
            columns[res_index++]->insert(part->getIndexSizeInBytes());