**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 column_size = getColumnSize(part_column.name, *part_column.type);
        if (column_size.data_compressed != 0 && !storage_columns.hasCompressionCodec(part_column.name))
        {
            String path_to_data_file;
            part_column.type->enumerateStreams([&](const IDataType::SubstreamPath & substream_path, const IDataType & )
            {
                if (path_to_data_file.empty())
                {
                    String candidate_path = getFullRelativePath() + IDataType::getFileNameForStream(part_column, substream_path) + ".bin";
                    
                    if (volume->getDisk()->exists(candidate_path) && volume->getDisk()->getFileSize(candidate_path) != 0)
                        path_to_data_file = candidate_path;
                }
            });
            if (path_to_data_file.empty())
            {
                LOG_WARNING(storage.log, "Part's {} column {} has non zero data compressed size, but all data files don't exist or empty", name, backQuoteIfNeed(part_column.name));
                continue;
            }
            result = getCompressionCodecForFile(volume->getDisk(), path_to_data_file);
            break;
        }
    }
    if (!result)
        result = CompressionCodecFactory::instance().getDefaultCodec();
    return result;
}
void IMergeTreeDataPart::loadPartitionAndMinMaxIndex()