**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

res.emplace_back(*it_to_delete);
            modifyPartState(it_to_delete, DataPartState::Deleting);
        }
    }
    if (!res.empty())
        LOG_TRACE(log, "Found {} old parts to remove.", res.size());
    return res;
}
void MergeTreeData::rollbackDeletingParts(const MergeTreeData::DataPartsVector & parts)
{
    auto lock = lockParts();
    for (const auto & part : parts)
    {
        
        part->assertState({DataPartState::Deleting});
        modifyPartState(part, DataPartState::Outdated);
    }
}
void MergeTreeData::removePartsFinally(const MergeTreeData::DataPartsVector & parts)
{
    {
        auto lock = lockParts();
        
        for (const auto & part : parts)
        {
            auto it = data_parts_by_info.find(part->info);
            if (it == data_parts_by_info.end())
                throw Exception("Deleting data part " + part->name + " doesn't exist", ErrorCodes::LOGICAL_ERROR);
            (*it)->assertState({DataPartState::Deleting});
            data_parts_indexes.erase(it);