**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

const auto & part = all_parts[part_number];
        auto part_state = all_parts_state[part_number];
        ColumnSize columns_size = part->getTotalColumnsSize();
        size_t src_index = 0, res_index = 0;
        if (columns_mask[src_index++])
        {
            WriteBufferFromOwnString out;
            part->partition.serializeText(*info.data, out, format_settings);
            columns[res_index++]->insert(out.str());
        }
        if (columns_mask[src_index++])
            columns[res_index++]->insert(part->name);
        if (columns_mask[src_index++])
            columns[res_index++]->insert(part->uuid);
        if (columns_mask[src_index++])
            columns[res_index++]->insert(part->getTypeName());
        if (columns_mask[src_index++])
            columns[res_index++]->insert(part_state == State::Committed);
        if (columns_mask[src_index++])
            columns[res_index++]->insert(part->getMarksCount());
        if (columns_mask[src_index++])
            columns[res_index++]->insert(part->rows_count);
        if (columns_mask[src_index++])
            columns[res_index++]->insert(part->getBytesOnDisk());
        if (columns_mask[src_index++])
            columns[res_index++]->insert(columns_size.data_compressed);
        if (columns_mask[src_index++])
            columns[res_index++]->insert(columns_size.data_uncompressed);
        if (columns_mask[src_index++])
            columns[res_index++]->insert(columns_size.marks);