```
play-eu :) SELECT actor_login, event_type, count() FROM github_events WHERE repo_name = 'ClickHouse/ClickHouse' GROUP BY actor_login, event_type WITH ROLLUP ORDER BY count() DESC LIMIT 10

SELECT
    actor_login,
    event_type,
    count()
FROM github_events
WHERE repo_name = 'ClickHouse/ClickHouse'
GROUP BY
    actor_login,
    event_type
    WITH ROLLUP
ORDER BY count() DESC
LIMIT 10

Query id: 1b7baa06-2ee6-4ae8-b1ed-4c9ecb21514c

Ok.
Exception on client:
Code: 36. DB::Exception: Code: 36. DB::Exception: Unexpected value 0 in enum. (BAD_ARGUMENTS) (version 22.5.1.1984 (official build)). (BAD_ARGUMENTS)
```
[[nodiscard]] virtual bool isDummy() const { return false; }
    /** Memory layout properties.
      *
      * Each value of a column can be placed in memory contiguously or not.
      *
      * Example: simple columns like UInt64 or FixedString store their values contiguously in single memory buffer.
      *
      * Example: Tuple store values of each component in separate subcolumn, so the values of Tuples with at least two components are not contiguous.
      * Another example is Nullable. Each value have null flag, that is stored separately, so the value is not contiguous in memory.
      *
      * There are some important cases, when values are not stored contiguously, but for each value, you can get contiguous memory segment,
      *  that will unambiguously identify the value. In this case, methods getDataAt and insertData are implemented.
      * Example: String column: bytes of strings are stored concatenated in one memory buffer
      *  and offsets to that buffer are stored in another buffer. The same is for Array of fixed-size contiguous elements.
      *
      * To avoid confusion between these cases, we don't have isContiguous method.
      */
    
    [[nodiscard]] virtual bool valuesHaveFixedSize() const { return isFixedAndContiguous(); }
    
    [[nodiscard]] virtual bool isFixedAndContiguous() const { return false; }
    
    [[nodiscard]] virtual StringRef getRawData() const { throw Exception("Column " + getName() + " is not a contiguous block of memory", ErrorCodes::NOT_IMPLEMENTED); }
    
    [[nodiscard]] virtual size_t sizeOfValueIfFixed() const { throw Exception("Values of column " + getName() + " are not fixed size.", ErrorCodes::CANNOT_GET_SIZE_OF_FIELD); }
    
    [[nodiscard]] virtual bool isNumeric() const { return false; }