**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

extern const int NO_SUCH_COLUMN_IN_TABLE;
    extern const int LOGICAL_ERROR;
    extern const int ILLEGAL_COLUMN;
    extern const int CORRUPTED_DATA;
    extern const int BAD_TYPE_OF_FIELD;
    extern const int BAD_ARGUMENTS;
    extern const int INVALID_PARTITION_VALUE;
    extern const int METADATA_MISMATCH;
    extern const int PART_IS_TEMPORARILY_LOCKED;
    extern const int TOO_MANY_PARTS;
    extern const int INCOMPATIBLE_COLUMNS;
    extern const int BAD_TTL_EXPRESSION;
    extern const int INCORRECT_FILE_NAME;
    extern const int BAD_DATA_PART_NAME;
    extern const int READONLY_SETTING;
    extern const int ABORTED;
    extern const int UNKNOWN_PART_TYPE;
    extern const int UNKNOWN_DISK;
    extern const int NOT_ENOUGH_SPACE;
    extern const int ALTER_OF_COLUMN_IS_FORBIDDEN;
    extern const int SUPPORT_IS_DISABLED;
    extern const int TOO_MANY_SIMULTANEOUS_QUERIES;
}
static void checkSampleExpression(const StorageInMemoryMetadata & metadata, bool allow_sampling_expression_not_in_primary_key)
{
    const auto & pk_sample_block = metadata.getPrimaryKey().sample_block;
    if (!pk_sample_block.has(metadata.sampling_key.column_names[0]) && !allow_sampling_expression_not_in_primary_key)
        throw Exception("Sampling expression must be present in the primary key", ErrorCodes::BAD_ARGUMENTS);
}
MergeTreeData::MergeTreeData(