**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

auto checksum = helper.hash_of_all_files;
                columns[res_index++]->insert(getHexUIntLowercase(checksum.first) + getHexUIntLowercase(checksum.second));
            }
            if (columns_mask[src_index++])
            {
                auto checksum = helper.hash_of_uncompressed_files;
                columns[res_index++]->insert(getHexUIntLowercase(checksum.first) + getHexUIntLowercase(checksum.second));
            }
            if (columns_mask[src_index++])
            {
                auto checksum = helper.uncompressed_hash_of_compressed_files;
                columns[res_index++]->insert(getHexUIntLowercase(checksum.first) + getHexUIntLowercase(checksum.second));
            }
        }
        
        if (columns_mask[src_index++])
            columns[res_index++]->insert(static_cast<UInt32>(part->ttl_infos.table_ttl.min));
        if (columns_mask[src_index++])
            columns[res_index++]->insert(static_cast<UInt32>(part->ttl_infos.table_ttl.max));
        auto add_ttl_info_map = [&](const TTLInfoMap & ttl_info_map)
        {
            Array expression_array;
            Array min_array;
            Array max_array;
            if (columns_mask[src_index])
                expression_array.reserve(ttl_info_map.size());
            if (columns_mask[src_index + 1])
                min_array.reserve(ttl_info_map.size());
            if (columns_mask[src_index + 2])
                max_array.reserve(ttl_info_map.size());