**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

void loadColumns(bool require);
    
    void loadChecksums(bool require);
    
    virtual void loadIndexGranularity();
    
    void loadIndex();
    
    
    void loadRowsCount();
    
    void loadTTLInfos();
    void loadPartitionAndMinMaxIndex();
    
    
    
    void loadDefaultCompressionCodec();
    
    
    CompressionCodecPtr detectDefaultCompressionCodec() const;
    mutable State state{State::Temporary};
};
using MergeTreeDataPartState = IMergeTreeDataPart::State;
using MergeTreeDataPartPtr = std::shared_ptr<const IMergeTreeDataPart>;
using MergeTreeMutableDataPartPtr = std::shared_ptr<IMergeTreeDataPart>;
bool isCompactPart(const MergeTreeDataPartPtr & data_part);
bool isWidePart(const MergeTreeDataPartPtr & data_part);
bool isInMemoryPart(const MergeTreeDataPartPtr & data_part);
}