**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

{
    PartsTemporaryRename renamed_parts(*this, "detached/");
    if (part)
    {
        String part_name = partition->as<ASTLiteral &>().value.safeGet<String>();
        validateDetachedPartName(part_name);
        renamed_parts.addPart(part_name, "deleting_" + part_name);
    }
    else
    {
        String partition_id = getPartitionIDFromQuery(partition, context);
        DetachedPartsInfo detached_parts = getDetachedParts();
        for (const auto & part_info : detached_parts)
            if (part_info.valid_name && part_info.partition_id == partition_id
                && part_info.prefix != "attaching" && part_info.prefix != "deleting")
                renamed_parts.addPart(part_info.dir_name, "deleting_" + part_info.dir_name);
    }
    LOG_DEBUG(log, "Will drop {} detached parts.", renamed_parts.old_and_new_names.size());
    renamed_parts.tryRenameAll();
    for (auto & [old_name, new_name] : renamed_parts.old_and_new_names)
    {
        const auto & [path, disk] = renamed_parts.old_part_name_to_path_and_disk[old_name];
        disk->removeRecursive(path + "detached/" + new_name + "/");
        LOG_DEBUG(log, "Dropped detached part {}", old_name);
        old_name.clear();
    }
}
MergeTreeData::MutableDataPartsVector MergeTreeData::tryLoadPartsToAttach(const ASTPtr & partition, bool attach_part,