**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

{
    String path = getFullRelativePath() + "columns.txt";
    auto metadata_snapshot = storage.getInMemoryMetadataPtr();
    NamesAndTypesList loaded_columns;
    if (!volume->getDisk()->exists(path))
    {
        
        if (require || part_type == Type::COMPACT)
            throw Exception("No columns.txt in part " + name + ", expected path " + path + " on drive " + volume->getDisk()->getName(),
                ErrorCodes::NO_FILE_IN_DATA_PART);
        
        for (const NameAndTypePair & column : metadata_snapshot->getColumns().getAllPhysical())
            if (volume->getDisk()->exists(getFullRelativePath() + getFileNameForColumn(column) + ".bin"))
                loaded_columns.push_back(column);
        if (columns.empty())
            throw Exception("No columns in part " + name, ErrorCodes::NO_FILE_IN_DATA_PART);
        {
            auto buf = volume->getDisk()->writeFile(path + ".tmp", 4096);
            loaded_columns.writeText(*buf);
        }
        volume->getDisk()->moveFile(path + ".tmp", path);
    }
    else
    {
        loaded_columns.readText(*volume->getDisk()->readFile(path));
    }
    setColumns(loaded_columns);
}
bool IMergeTreeDataPart::shallParticipateInMerges(const StoragePolicyPtr & storage_policy) const