**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

ErrorCodes::READONLY_SETTING};
            }
            if (!current_value && MergeTreeSettings::isPartFormatSetting(setting_name))
            {
                MergeTreeSettings copy = *getSettings();
                copy.applyChange(changed_setting);
                String reason;
                if (!canUsePolymorphicParts(copy, &reason) && !reason.empty())
                    throw Exception("Can't change settings. Reason: " + reason, ErrorCodes::NOT_IMPLEMENTED);
            }
            if (setting_name == "storage_policy")
                checkStoragePolicy(global_context.getStoragePolicy(new_value.safeGet<String>()));
        }
    }
    for (const auto & part : getDataPartsVector())
    {
        bool at_least_one_column_rest = false;
        for (const auto & column : part->getColumns())
        {
            if (!dropped_columns.count(column.name))
            {
                at_least_one_column_rest = true;
                break;
            }
        }
        if (!at_least_one_column_rest)
        {
            std::string postfix;
            if (dropped_columns.size() > 1)
                postfix = "s";