**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 (!attach || !version_file_exists)
    {
        format_version = min_format_version;
        auto buf = version_file.second->writeFile(version_file.first);
        writeIntText(format_version.toUnderType(), *buf);
        if (global_context.getSettingsRef().fsync_metadata)
            buf->sync();
    }
    else
    {
        auto buf = version_file.second->readFile(version_file.first);
        UInt32 read_format_version;
        readIntText(read_format_version, *buf);
        format_version = read_format_version;
        if (!buf->eof())
            throw Exception("Bad version file: " + fullPath(version_file.second, version_file.first), ErrorCodes::CORRUPTED_DATA);
    }
    if (format_version < min_format_version)
    {
        if (min_format_version == MERGE_TREE_DATA_MIN_FORMAT_VERSION_WITH_CUSTOM_PARTITIONING.toUnderType())
            throw Exception(
                "MergeTree data format version on disk doesn't support custom partitioning",
                ErrorCodes::METADATA_MISMATCH);
    }
    String reason;
    if (!canUsePolymorphicParts(*settings, &reason) && !reason.empty())
        LOG_WARNING(log, "{} Settings 'min_rows_for_wide_part', 'min_bytes_for_wide_part', "
            "'min_rows_for_compact_part' and 'min_bytes_for_compact_part' will be ignored.", reason);
}
StoragePolicyPtr MergeTreeData::getStoragePolicy() const