[UUID 6/8] UUID multi-stage engine (planner + runtime)

[xiangfu0]

What

Multi-stage (v2) engine support for UUID.

Changes

• expressions.proto UUID / UUID_ARRAY enum values + planner type resolution, Rex parsing, proto serde, TypeFactory
• HashJoinOperator / EnrichedHashJoinOperator + UuidLookupTable (LookupTable.normalizeKey), OneUuidKeyGroupIdGenerator, ServerPlanRequestUtils

Enables

UUID equi-joins and group-by in the multi-stage engine.

⚠️ Rolling-upgrade note: the new proto enum values are unknown to older brokers/servers; multi-stage queries with UUID literals fail on mixed-version clusters. Atomic-upgrade feature.

Depends on

#18869 and #18871.

About this PR / how to review

This is part 6 of 8 splitting #18140 (first-class logical UUID type) into layered PRs, as requested there.

The split is enabled by the v1 design: DataType.UUID has stored type BYTES, so most paths handle it automatically; each PR adds explicit UUID semantics to one subsystem. Head branch lives on xiangfu0/pinot.

This PR is stacked on #18873 (branch uuid-split/05-agg-groupby-distinct). Because GitHub PRs to apache must base on master, the Files-changed tab is cumulative (it includes layers 1–6) until the PRs below it merge. Review the commit titled [UUID 6/8] UUID multi-stage engine (planner + runtime) — that is this layer's change. Each parent merge shrinks this diff after a rebase.

Full stack (merge bottom → top)

1. [UUID 1/8] Add logical UUID type foundation (pinot-spi) #18869 — [UUID 1/8] logical UUID type foundation (pinot-spi)
2. [UUID 2/8] UUID ingest and segment storage #18870 — [UUID 2/8] UUID ingest and segment storage
3. [UUID 3/8] UUID result rendering (DataSchema, Arrow/JSON encoders) #18871 — [UUID 3/8] UUID result rendering (DataSchema, Arrow/JSON encoders)
4. [UUID 4/8] UUID server-side predicates, CAST and transforms #18872 — [UUID 4/8] UUID server-side predicates, CAST and transforms
5. [UUID 5/8] UUID aggregation, group-by and distinct #18873 — [UUID 5/8] UUID aggregation, group-by and distinct
6. [UUID 6/8] UUID multi-stage engine (planner + runtime) #18874 — [UUID 6/8] UUID multi-stage engine (planner + runtime)
7. [UUID 7/8] UUID scalar UDFs and partitioning #18875 — [UUID 7/8] UUID scalar UDFs and partitioning
8. [UUID 8/8] UUID integration tests, benchmarks and docs #18876 — [UUID 8/8] UUID integration tests, benchmarks and docs

After #18869 lands, PRs 2/4/7 (#18870, #18872, #18875) only depend on it and can be reviewed in parallel; PRs 5/6 (#18873, #18874) also need #18871; PR 8 (#18876) needs #18874.

Full feature description, v1 design contract, scope exclusions, and benchmark numbers: #18140.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 52.28426% with 564 lines in your changes missing coverage. Please review.
✅ Project coverage is 64.85%. Comparing base (b6c3ca6) to head (636f7d9).
⚠️ Report is 13 commits behind head on master.

Files with missing lines	Patch %	Lines
...ot/common/request/context/RequestContextUtils.java	55.30%	48 Missing and 11 partials ⚠️
...java/org/apache/pinot/common/utils/DataSchema.java	55.55%	36 Missing and 8 partials ⚠️
...ator/transform/function/CastTransformFunction.java	34.92%	40 Missing and 1 partial ⚠️
...sform/function/ScalarTransformFunctionWrapper.java	17.07%	34 Missing ⚠️
...pby/NoDictionarySingleColumnGroupKeyGenerator.java	42.00%	23 Missing and 6 partials ⚠️
.../function/DistinctCountULLAggregationFunction.java	0.00%	26 Missing ⚠️
...perator/query/NonScanBasedAggregationOperator.java	20.00%	22 Missing and 2 partials ⚠️
...ion/DistinctCountCPCSketchAggregationFunction.java	0.00%	24 Missing ⚠️
...upby/NoDictionaryMultiColumnGroupKeyGenerator.java	26.66%	19 Missing and 3 partials ⚠️
...e/operator/groupby/OneUuidKeyGroupIdGenerator.java	0.00%	20 Missing ⚠️
... and 36 more

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #18874      +/-   ##
============================================
- Coverage     64.89%   64.85%   -0.04%     
  Complexity     1347     1347              
============================================
  Files          3398     3401       +3     
  Lines        212550   213561    +1011     
  Branches      33503    33724     +221     
============================================
+ Hits         137927   138507     +580     
- Misses        63481    63848     +367     
- Partials      11142    11206      +64     

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	64.85% <52.28%> (-0.04%)	⬇️
temurin	64.85% <52.28%> (-0.04%)	⬇️
unittests	64.85% <52.28%> (-0.04%)	⬇️
unittests1	56.83% <41.20%> (-0.05%)	⬇️
unittests2	37.17% <18.44%> (-0.09%)	⬇️

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