**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 (!ttl_infos.rows_where_ttl.count(rows_where_desc.result_column))
            return false;
    }
    return true;
}
String IMergeTreeDataPart::getUniqueId() const
{
    String id;
    auto disk = volume->getDisk();
    if (disk->getType() == DB::DiskType::Type::S3)
        id = disk->getUniqueId(getFullRelativePath() + "checksums.txt");
    if (id.empty())
        throw Exception("Can't get unique S3 object", ErrorCodes::LOGICAL_ERROR);
    return id;
}
bool isCompactPart(const MergeTreeDataPartPtr & data_part)
{
    return (data_part && data_part->getType() == MergeTreeDataPartType::COMPACT);
}
bool isWidePart(const MergeTreeDataPartPtr & data_part)
{
    return (data_part && data_part->getType() == MergeTreeDataPartType::WIDE);
}
bool isInMemoryPart(const MergeTreeDataPartPtr & data_part)
{
    return (data_part && data_part->getType() == MergeTreeDataPartType::IN_MEMORY);
}
}