**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(part->name);
            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);
            if (columns_mask[src_index++])
                columns[res_index++]->insert(UInt64(part->modification_time));
            if (columns_mask[src_index++])
                columns[res_index++]->insert(UInt64(part->remove_time.load(std::memory_order_relaxed)));
            if (columns_mask[src_index++])
                columns[res_index++]->insert(UInt64(use_count));
            if (columns_mask[src_index++])
                columns[res_index++]->insert(min_date);
            if (columns_mask[src_index++])
                columns[res_index++]->insert(max_date);
            if (columns_mask[src_index++])