**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

const StorageMetadataPtr & metadata_snapshot,
    const PartitionCommands & commands,
    const Context & query_context)
{
    PartitionCommandsResultInfo result;
    for (const PartitionCommand & command : commands)
    {
        PartitionCommandsResultInfo current_command_results;
        switch (command.type)
        {
            case PartitionCommand::DROP_PARTITION:
                if (command.part)
                    checkPartCanBeDropped(command.partition);
                else
                    checkPartitionCanBeDropped(command.partition);
                dropPartition(command.partition, command.detach, command.part, query_context);
                break;
            case PartitionCommand::DROP_DETACHED_PARTITION:
                dropDetached(command.partition, command.part, query_context);
                break;
            case PartitionCommand::ATTACH_PARTITION:
                current_command_results = attachPartition(command.partition, metadata_snapshot, command.part, query_context);
                break;
            case PartitionCommand::MOVE_PARTITION:
            {
                switch (*command.move_destination_type)
                {