**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

{
                return column_to_sum == Nested::extractTableName(name_and_type.name);
            };
            if (columns.end() == std::find_if(columns.begin(), columns.end(), check_column_to_sum_exists))
                throw Exception(
                        "Column " + column_to_sum + " listed in columns to sum does not exist in table declaration.", ErrorCodes::NO_SUCH_COLUMN_IN_TABLE);
        }
        
        if (metadata.isPartitionKeyDefined())
        {
            auto partition_key_columns = metadata.getPartitionKey().column_names;
            Names names_intersection;
            std::set_intersection(columns_to_sum.begin(), columns_to_sum.end(),
                                  partition_key_columns.begin(), partition_key_columns.end(),
                                  std::back_inserter(names_intersection));
            if (!names_intersection.empty())
                throw Exception("Columns: " + boost::algorithm::join(names_intersection, ", ") +
                " listed both in columns to sum and in partition key. That is not allowed.", ErrorCodes::BAD_ARGUMENTS);
        }
    }
    if (mode == MergingParams::Replacing)
        check_version_column(true, "ReplacingMergeTree");
    if (mode == MergingParams::VersionedCollapsing)
    {
        check_sign_column(false, "VersionedCollapsingMergeTree");
        check_version_column(false, "VersionedCollapsingMergeTree");
    }
    
}
String MergeTreeData::MergingParams::getModeName() const