Sequelize to handle WITH ROLLUP group by's (MySQL)

Hi good folks,

Let me introduce the ROLLUP feature from MySQL 5.5+ with examples:

Simple GROUP BY sum:

mysql> SELECT year, SUM(profit) FROM sales GROUP BY year;
+------+-------------+
| year | SUM(profit) |
+------+-------------+
| 2000 |        4525 |
| 2001 |        3010 |
+------+-------------+

Adding a WITH ROLLUP modifier to the GROUP BY clause causes the query to produce another row that shows the grand total over all (grouped up) values

mysql> SELECT year, SUM(profit) FROM sales GROUP BY year WITH ROLLUP;
+------+-------------+
| year | SUM(profit) |
+------+-------------+
| 2000 |        4525 |
| 2001 |        3010 |
| NULL |        7535 |
+------+-------------+

http://dev.mysql.com/doc/refman/5.7/en/group-by-modifiers.html

So, this is a nice featurette that I think would be fun for reports. But, I wasn't able to use on Sequelize because it is not recognized (not even cited on Docs) and so, even forcing it to include that clause after the last group item with Sequelize.literal it was not included on group arrays.

I think it could be set as (regarding the above example):

Sales.findAll({
  attributes: ['year', [Sequelize.fn('SUM', Sequelize.col('profit')), 'profitSum'],
  group: ['year'],
  rollup: true
})

Resulting in an new array item as:

[
  {year: 2000, profitSum: 4525},
  {year: 2001, profitSum: 3010},
  {year: null, profitSum: 7535, summary: true}
]

Rollup also replaces ORDER BY clause, so it would be excludent with order param.

What do you think of that?

Begin with the Sales.findAll options shown and trace how group arrays and Sequelize.literal are handled for MySQL. The proposed rollup option, interaction with order, and summary field need agreement before implementation. Done would require a settled API and tests covering the generated query and returned rows.