Support GROUPING SETS

[novikd]

Changelog category (leave one):

• New Feature

Changelog entry (a user-readable short description of the changes that goes to CHANGELOG.md):

Add support of GROUPING SETS in GROUP BY clause. Follow up after #33186. This implementation supports a parallel processing of grouping sets.

[KochetovNicolai]

For some reason, I have an extra space while formatting in client:

ELECT
    SUM(number) AS sum_value,
    count() AS count_value
FROM numbers_mt(1000000)
GROUP BY
    GROUPING SETS (
    ( number % 10),
     ^ here
    ( number % 100))
     ^ here
ORDER BY
    sum_value ASC,
    count_value ASC

[novikd]

It's fixed in #32999

[KochetovNicolai]

Compare result for

SELECT
    k1,
    k2,
    SUM(number) AS sum_value,
    count() AS count_value
FROM numbers(6)
GROUP BY
    GROUPING SETS (
    ( number % 2 AS k1),
    ( number % 3 AS k2))
ORDER BY
    sum_value ASC,
    count_value ASC

Query id: 080ee3d9-1856-41af-9185-775663655c71

┌─k1─┬─k2─┬─sum_value─┬─count_value─┐
│  0 │  0 │         3 │           2 │
│  0 │  1 │         5 │           2 │
│  0 │  0 │         6 │           3 │
│  0 │  2 │         7 │           2 │
│  1 │  0 │         9 │           3 │
└────┴────┴───────────┴─────────────┘

and

SELECT
    k1,
    k2,
    SUM(number) AS sum_value,
    count() AS count_value
FROM remote('127.0.0.{2,3}', numbers(6))
GROUP BY
    GROUPING SETS (
    ( number % 2 AS k1),
    ( number % 3 AS k2))
ORDER BY
    sum_value ASC,
    count_value ASC

Query id: 5fc9bf53-4389-4e9b-b4ab-4cee8ba5e082

┌─k1─┬─k2─┬─sum_value─┬─count_value─┐
│  0 │  1 │        10 │           4 │
│  0 │  2 │        14 │           4 │
│  1 │  0 │        18 │           6 │
│  0 │  0 │        18 │          10 │
└────┴────┴───────────┴─────────────┘

The key (0, 0) was squashed.
That's why we also need __grouping column for intermediate header (and merging transform should use in as an additional key)

[KochetovNicolai]

Generally everything is ok.
Except it would be good to fix key squashing for the distributed case :)

[novikd]

@Mergifyio update

[mergify]

update

✅ Branch has been successfully updated

[KochetovNicolai]

ok, failed tests does not seem to be relevant to the PR, merging.