**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

{
    auto disk = getDiskForPart(part_name, additional_path);
    if (disk)
        return relative_data_path + additional_path;
    return {};
}
Strings MergeTreeData::getDataPaths() const
{
    Strings res;
    auto disks = getStoragePolicy()->getDisks();
    for (const auto & disk : disks)
        res.push_back(getFullPathOnDisk(disk));
    return res;
}
MergeTreeData::PathsWithDisks MergeTreeData::getRelativeDataPathsWithDisks() const
{
    PathsWithDisks res;
    auto disks = getStoragePolicy()->getDisks();
    for (const auto & disk : disks)
        res.emplace_back(relative_data_path, disk);
    return res;
}
MergeTreeData::MatcherFn MergeTreeData::getPartitionMatcher(const ASTPtr & partition_ast, const Context & context) const