**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 backup_path = std::filesystem::path("shadow") / escapeForFileName(backup_name) / relative_data_path;
    LOG_DEBUG(log, "Unfreezing parts by path {}", backup_path.generic_string());
    PartitionCommandsResultInfo result;
    for (const auto & disk : getStoragePolicy()->getDisks())
    {
        if (!disk->exists(backup_path))
            continue;
        for (auto it = disk->iterateDirectory(backup_path); it->isValid(); it->next())
        {
            const auto & partition_directory = it->name();
            
            auto found = partition_directory.find('_');
            if (found == std::string::npos)
                continue;
            auto partition_id = partition_directory.substr(0, found);
            if (!matcher(partition_id))
                continue;
            const auto & path = it->path();
            disk->removeRecursive(path);
            result.push_back(PartitionCommandResultInfo{
                .partition_id = partition_id,
                .part_name = partition_directory,
                .backup_path = disk->getPath() + backup_path.generic_string(),