**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

{
    if (!isStoredOnDisk())
        return;
    if (relative_path.empty())
        throw Exception("Part relative_path cannot be empty. This is bug.", ErrorCodes::LOGICAL_ERROR);
    /** Atomic directory removal:
      * - rename directory to temporary name;
      * - remove it recursive.
      *
      * For temporary name we use "delete_tmp_" prefix.
      *
      * NOTE: We cannot use "tmp_delete_" prefix, because there is a second thread,
      *  that calls "clearOldTemporaryDirectories" and removes all directories, that begin with "tmp_" and are old enough.
      * But when we removing data part, it can be old enough. And rename doesn't change mtime.
      * And a race condition can happen that will lead to "File not found" error here.