**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

merging_params.check(metadata_);
    if (metadata_.sampling_key.definition_ast != nullptr)
    {
        
        checkSampleExpression(metadata_, attach || settings->compatibility_allow_sampling_expression_not_in_primary_key);
    }
    checkTTLExpressions(metadata_, metadata_);
    
    PathWithDisk version_file;
    
    for (const auto & [path, disk] : getRelativeDataPathsWithDisks())
    {
        disk->createDirectories(path);
        disk->createDirectories(path + MergeTreeData::DETACHED_DIR_NAME);
        auto current_version_file_path = path + MergeTreeData::FORMAT_VERSION_FILE_NAME;
        if (disk->exists(current_version_file_path))
        {
            if (!version_file.first.empty())
            {
                LOG_ERROR(log, "Duplication of version file {} and {}", fullPath(version_file.second, version_file.first), current_version_file_path);
                throw Exception("Multiple format_version.txt file", ErrorCodes::CORRUPTED_DATA);
            }
            version_file = {current_version_file_path, disk};
        }
    }
    
    if (version_file.first.empty())
        version_file = {relative_data_path + MergeTreeData::FORMAT_VERSION_FILE_NAME, getStoragePolicy()->getAnyDisk()};
    bool version_file_exists = version_file.second->exists(version_file.first);