**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

{
    for (const auto & column : part->getColumns())
    {
        ColumnSize & total_column_size = column_sizes[column.name];
        ColumnSize part_column_size = part->getColumnSize(column.name, *column.type);
        total_column_size.add(part_column_size);
    }
}
void MergeTreeData::removePartContributionToColumnSizes(const DataPartPtr & part)
{
    for (const auto & column : part->getColumns())
    {
        ColumnSize & total_column_size = column_sizes[column.name];
        ColumnSize part_column_size = part->getColumnSize(column.name, *column.type);
        auto log_subtract = [&](size_t & from, size_t value, const char * field)
        {
            if (value > from)
                LOG_ERROR(log, "Possibly incorrect column size subtraction: {} - {} = {}, column: {}, field: {}",
                    from, value, from - value, column.name, field);
            from -= value;
        };
        log_subtract(total_column_size.data_compressed, part_column_size.data_compressed, ".data_compressed");
        log_subtract(total_column_size.data_uncompressed, part_column_size.data_uncompressed, ".data_uncompressed");
        log_subtract(total_column_size.marks, part_column_size.marks, ".marks");
    }
}
void MergeTreeData::checkAlterPartitionIsPossible(const PartitionCommands & commands, const StorageMetadataPtr & , const Settings & settings) const