**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 (!checkState(affordable_states))
    {
        String states_str;
        for (auto affordable_state : affordable_states)
            states_str += stateToString(affordable_state) + " ";
        throw Exception("Unexpected state of part " + getNameWithState() + ". Expected: " + states_str, ErrorCodes::NOT_FOUND_EXPECTED_DATA_PART);
    }
}
void IMergeTreeDataPart::assertOnDisk() const
{
    if (!isStoredOnDisk())
        throw Exception("Data part '" + name + "' with type '"
            + getType().toString() + "' is not stored on disk", ErrorCodes::LOGICAL_ERROR);
}
UInt64 IMergeTreeDataPart::getMarksCount() const
{
    return index_granularity.getMarksCount();
}
size_t IMergeTreeDataPart::getFileSizeOrZero(const String & file_name) const
{
    auto checksum = checksums.files.find(file_name);
    if (checksum == checksums.files.end())
        return 0;
    return checksum->second.file_size;
}
String IMergeTreeDataPart::getColumnNameWithMinimumCompressedSize(const StorageMetadataPtr & metadata_snapshot) const