Support SQL GROUPING SETS / ROLLUP / CUBE on both query engines

[xiangfu0]

Summary

Adds SQL GROUPING SETS / ROLLUP / CUBE and the GROUPING() / GROUPING_ID() indicator functions, working end-to-end on both query engines.

Single-stage engine (SSE) — native, single scan

• New optional Thrift field PinotQuery.groupingSetsMasks carries the per-set participation masks over the union of group-by columns.
• CalciteSqlParser normalizes ROLLUP / CUBE / GROUPING SETS (including mixed forms like a, ROLLUP(b, c)) into the union columns + masks, and rewrites GROUPING(col) / GROUPING_ID(...) onto a synthetic internal $groupingId key column.
• GroupingSetsGroupKeyGenerator maps each row to one group per set (via the existing multi-valued group-by path), with $groupingId as an extra key column that keeps a rolled-up NULL from colliding with a real-data NULL.
• The combine/reduce path is migrated from N to N+1 key columns, and the NULL-bitmap serialization path is forced on for rolled-up columns so they round-trip as NULL regardless of null-handling mode. Star-tree is disabled for these queries.

Multi-stage engine (MSE) — UNION ALL expansion

• A grouping-set LogicalAggregate is expanded into a UNION ALL of ordinary per-set aggregates (GroupingSetsExpander), with rolled-up columns projected as NULL and GROUPING() / GROUPING_ID() computed as per-branch constant literals. The multi-stage runtime therefore executes only standard Union / Aggregate / Project plans and needs no runtime changes.
• GROUPING / GROUPING_ID registered in PinotOperatorTable; ROW-expression validation relaxed for the parenthesized grouping lists.

Example

SELECT country, city, SUM(sales), GROUPING(country), GROUPING(city)
FROM   sales
GROUP  BY ROLLUP(country, city)

returns the detail rows, per-country subtotals (city = NULL, GROUPING(city) = 1), and the grand total (country/city = NULL, GROUPING = 1).

Testing

• Unit tests: bit conventions, scalar functions, parser normalization + GROUPING rewrite, Thrift wire round-trip.
• In-process server-execution + broker-reduce tests (GroupingSetsQueriesTest), covering ROLLUP/CUBE/GROUPING SETS, GROUPING/GROUPING_ID, HAVING, both ORDER BY paths, the empty-server schema, and the multi-valued-column rejection.
• MSE planner tests (GroupingSetsPlannerTest) + 191 existing planner tests (no regression).
• Cluster integration test (GroupingSetsTest) running every query on both engines.

Limitations / follow-ups

• Multi-valued group-by columns inside grouping sets are rejected with a clear error (single-valued only for now).
• The new groupingSetsMasks Thrift field is optional and wire-compatible, but grouping-set queries require all servers to be upgraded: an un-upgraded server would ignore the field and run a plain GROUP BY. This is a new query capability (no existing-query regression) and should be noted in release notes; a broker-side min-version gate is a sensible follow-up.

🤖 Generated with Claude Code

[codecov-commenter]

Codecov Report

❌ Patch coverage is 88.33333% with 49 lines in your changes missing coverage. Please review.
✅ Project coverage is 64.49%. Comparing base (5dee072) to head (94aab3e).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
...egation/groupby/GroupingSetsGroupKeyGenerator.java	72.80%	21 Missing and 10 partials ⚠️
...org/apache/pinot/sql/parsers/CalciteSqlParser.java	89.92%	4 Missing and 9 partials ⚠️
...apache/pinot/calcite/rel/GroupingSetsExpander.java	95.08%	1 Missing and 2 partials ⚠️
...operator/combine/SortedGroupByCombineOperator.java	50.00%	0 Missing and 1 partial ⚠️
...pinot/core/query/request/context/QueryContext.java	88.88%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #18664      +/-   ##
============================================
+ Coverage     56.88%   64.49%   +7.60%     
- Complexity        7     1291    +1284     
============================================
  Files          2582     3371     +789     
  Lines        149911   208775   +58864     
  Branches      24234    32652    +8418     
============================================
+ Hits          85283   134653   +49370     
- Misses        57415    63294    +5879     
- Partials       7213    10828    +3615     

Flag	Coverage Δ
custom-integration1	100.00% <ø> (ø)
integration	100.00% <ø> (ø)
integration1	100.00% <ø> (ø)
integration2	0.00% <ø> (ø)
java-21	64.49% <88.33%> (+7.60%)	⬆️
temurin	64.49% <88.33%> (+7.60%)	⬆️
unittests	64.49% <88.33%> (+7.60%)	⬆️
unittests1	56.95% <88.33%> (+0.06%)	⬆️
unittests2	37.07% <12.85%> (?)

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