**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

const MergeTreeData & storage;
    String name;
    MergeTreePartInfo info;
    
    
    
    UUID uuid = UUIDHelpers::Nil;
    VolumePtr volume;
    
    
    mutable String relative_path;
    MergeTreeIndexGranularityInfo index_granularity_info;
    size_t rows_count = 0;
    time_t modification_time = 0;
    
    mutable std::atomic<time_t> remove_time { std::numeric_limits<time_t>::max() };
    
    bool is_temp = false;
    
    bool is_duplicate = false;
    
    mutable std::atomic<bool> is_frozen {false};
    /**
     * Part state is a stage of its lifetime. States are ordered and state of a part could be increased only.
     * Part state should be modified under data_parts mutex.
     *
     * Possible state transitions:
     * Temporary -> Precommitted:   we are trying to commit a fetched, inserted or merged part to active set
     * Precommitted -> Outdated:    we could not to add a part to active set and doing a rollback (for example it is duplicated part)