**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 String partition_id = getPartitionIDFromQuery(partition, global_context);
    auto parts_to_remove = getDataPartsVectorInPartition(MergeTreeDataPartState::Committed, partition_id);
    UInt64 partition_size = 0;
    for (const auto & part : parts_to_remove)
        partition_size += part->getBytesOnDisk();
    auto table_id = getStorageID();
    global_context.checkPartitionCanBeDropped(table_id.database_name, table_id.table_name, partition_size);
}
void MergeTreeData::checkPartCanBeDropped(const ASTPtr & part_ast)
{
    String part_name = part_ast->as<ASTLiteral &>().value.safeGet<String>();
    auto part = getPartIfExists(part_name, {MergeTreeDataPartState::Committed});
    if (!part)
        throw Exception(ErrorCodes::NO_SUCH_DATA_PART, "No part {} in committed state", part_name);
    auto table_id = getStorageID();
    global_context.checkPartitionCanBeDropped(table_id.database_name, table_id.table_name, part->getBytesOnDisk());
}
void MergeTreeData::movePartitionToDisk(const ASTPtr & partition, const String & name, bool moving_part, const Context & context)