**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 & [expression, ttl_info] : ttl_info_map)
            {
                if (columns_mask[src_index])
                    expression_array.emplace_back(expression);
                if (columns_mask[src_index + 1])
                    min_array.push_back(static_cast<UInt32>(ttl_info.min));
                if (columns_mask[src_index + 2])
                    max_array.push_back(static_cast<UInt32>(ttl_info.max));
            }
            if (columns_mask[src_index++])
                columns[res_index++]->insert(expression_array);
            if (columns_mask[src_index++])
                columns[res_index++]->insert(min_array);
            if (columns_mask[src_index++])
                columns[res_index++]->insert(max_array);
        };
        add_ttl_info_map(part->ttl_infos.moves_ttl);
        if (columns_mask[src_index++])
            columns[res_index++]->insert(queryToString(part->default_codec->getCodecDesc()));
        add_ttl_info_map(part->ttl_infos.recompression_ttl);
        add_ttl_info_map(part->ttl_infos.group_by_ttl);
        add_ttl_info_map(part->ttl_infos.rows_where_ttl);
        
        
        if (has_state_column)
            columns[res_index++]->insert(IMergeTreeDataPart::stateToString(part_state));
    }
}
}