**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 (!other.initialized)
        return;
    if (!initialized)
    {
        hyperrectangle = other.hyperrectangle;
        initialized = true;
    }
    else
    {
        for (size_t i = 0; i < hyperrectangle.size(); ++i)
        {
            hyperrectangle[i].left = std::min(hyperrectangle[i].left, other.hyperrectangle[i].left);
            hyperrectangle[i].right = std::max(hyperrectangle[i].right, other.hyperrectangle[i].right);
        }
    }
}
static void incrementStateMetric(IMergeTreeDataPart::State state)