expression support for grouping(a,b,c,...) with maximum of 64 parameters

[AilinKid]

Enhancement

add one more dimension for grouping marks maintenance.

ideas come from MySQL's support for grouping(a,b,c,...) with maximum of 64 parameters.

mysql> select grouping(a,b), grouping(a), grouping(b) from t group by a, b with rollup;
+---------------+-------------+-------------+
| grouping(a,b) | grouping(a) | grouping(b) |
+---------------+-------------+-------------+
|             0 |           0 |           0 |
|             1 |           0 |           1 |
|             0 |           0 |           0 |
|             1 |           0 |           1 |
|             3 |           1 |           1 |
+---------------+-------------+-------------+
5 rows in set (0.00 sec)
mysql> select grouping(b,a), grouping(a), grouping(b) from t group by a, b with rollup;
+---------------+-------------+-------------+
| grouping(b,a) | grouping(a) | grouping(b) |
+---------------+-------------+-------------+
|             0 |           0 |           0 |
|             2 |           0 |           1 |
|             0 |           0 |           0 |
|             2 |           0 |           1 |
|             3 |           1 |           1 |
+---------------+-------------+-------------+
5 rows in set (0.00 sec)

Notice the result difference of grouping(a,b) and grouping(b,a)!

mysql reference

As seen here, if GROUPING (a,b) returns 3, it means that NULL in column “a” and NULL in column “b” for that row is produce by a ROLLUP operation. If result is 1, NULL in column “b” alone is a result of ROLLUP operation.
https://dev.mysql.com/blog-archive/mysql-8-0-grouping-function/

when evaluating the grouping function's value, the formula is:

grouping(a,b,c) = grouping(a)<<2 + grouping(b)<<1 << grouping(c)

the left shift size is exactly according to their listed position in the grouping function.
so we should maintain all the grouping marks (for every single col) down, and add one more round computation for the left shift plus if the len(groupingMarks) is greater than 1 (means multi col args in grouping function).

[AilinKid]

pingcap/tiflash#7590 related tiflash issue