**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

{
    old_and_new_names.push_back({old_name, new_name});
    for (const auto & [path, disk] : storage.getRelativeDataPathsWithDisks())
    {
        for (auto it = disk->iterateDirectory(path + source_dir); it->isValid(); it->next())
        {
            if (it->name() == old_name)
            {
                old_part_name_to_path_and_disk[old_name] = {path, disk};
                break;
            }
        }
    }
}
void MergeTreeData::PartsTemporaryRename::tryRenameAll()