**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 (parts_mover.moves_blocker.isCancelled())
        return false;
    auto moving_tagger = checkPartsForMove(parts, space);
    if (moving_tagger->parts_to_move.empty())
        return false;
    return moveParts(moving_tagger);
}
MergeTreeData::CurrentlyMovingPartsTaggerPtr MergeTreeData::selectPartsForMove()
{
    MergeTreeMovingParts parts_to_move;
    auto can_move = [this](const DataPartPtr & part, String * reason) -> bool
    {
        if (partIsAssignedToBackgroundOperation(part))
        {
            *reason = "part already assigned to background operation.";
            return false;
        }
        if (currently_moving_parts.count(part))
        {
            *reason = "part is already moving.";
            return false;
        }
        return true;
    };
    std::lock_guard moving_lock(moving_parts_mutex);
    parts_mover.selectPartsForMove(parts_to_move, can_move, moving_lock);
    return std::make_shared<CurrentlyMovingPartsTagger>(std::move(parts_to_move), *this);
}
MergeTreeData::CurrentlyMovingPartsTaggerPtr MergeTreeData::checkPartsForMove(const DataPartsVector & parts, SpacePtr space)