chore(amber): remove the deprecated ExpansionGreedyScheduleGenerator

[aglinxinyuan]

What changes were proposed in this PR?

Acts on the removal notice ExpansionGreedyScheduleGenerator has carried since #3542. Pure deletion of the class and its spec, no behaviour change: −832 lines.

#3144 ("Refactoring of Schedule Generation", 2024-12-14) made CostBasedScheduleGenerator the only generator the engine constructs. #3542 (2025-07-09) then annotated the greedy one with the notice it still carries today:

This greedy schedule generator will be removed in the future. Use CostBasedScheduleGenerator instead.

WorkflowScheduler.scala:46 -> new CostBasedScheduleGenerator(...)   (live, untouched)
                              ExpansionGreedyScheduleGenerator      (unreachable since #3144)

No configuration can bring it back: the schedule-generator block in application.conf holds only CostBased tuning parameters (max-concurrent-regions, use-global-search, use-top-down-search, search-timeout, read at ApplicationConfig.scala:87-90), with no generator-selection key.

Reviewer note: the abstract base ScheduleGenerator is not touched — CostBasedScheduleGenerator extends it and is unaffected. Only the greedy subclass and its spec are removed.

Any related issues, documentation, discussions?

Closes #7444

How was this PR tested?

Existing tests only — this PR adds none, since it removes code and the spec that covered it.

Locally, from the repo root with Java 17:

• sbt "WorkflowExecutionService/Test/compile" — success (main and test sources).

Verification that nothing references the removed class, re-runnable by a reviewer:

git grep -n ExpansionGreedy          # only the two deleted files
git grep -in greedy -- '*.conf' '*.yml' '*.yaml' '*.json' '*.properties'   # no generator-selection key

Was this PR authored or co-authored using generative AI tooling?

Generated-by: Claude Code (Claude Opus 5)

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⚠️ Benchmark changes need a look

🟢 0 better · 🔴 8 worse · ⚪ 7 noise (<±5%) · 0 without baseline

Compared against main e03d971 benchmarked on this same runner, so the delta is largely free of cross-runner hardware noise. The "7d avg" column still reflects the gh-pages dashboard. Treat <±5% as noise unless repeated.

Dashboard · Run

	config	throughput	MB/s	latency	max Δ latest / 7d
🔴	bs=10 sw=10 sl=64	373	0.228	24,280/37,959/37,959 us	🔴 +24.8% / 🔴 +135.5%
🔴	bs=100 sw=10 sl=64	870	0.531	108,338/171,711/171,711 us	🔴 +11.4% / 🔴 +54.4%
🔴	bs=1000 sw=10 sl=64	1,092	0.666	903,921/1,058,331/1,058,331 us	🔴 +8.2% / 🟢 -11.8%

Baseline details

Latest main e03d971 from same runner

config	metric	PR	latest main	7d avg	Δ latest	Δ 7d
bs=10 sw=10 sl=64	throughput	373 tuples/sec	437 tuples/sec	752.25 tuples/sec	-14.6%	-50.4%
bs=10 sw=10 sl=64	MB/s	0.228 MB/s	0.267 MB/s	0.459 MB/s	-14.6%	-50.3%
bs=10 sw=10 sl=64	p50	24,280 us	23,798 us	13,006 us	+2.0%	+86.7%
bs=10 sw=10 sl=64	p95	37,959 us	30,418 us	16,117 us	+24.8%	+135.5%
bs=10 sw=10 sl=64	p99	37,959 us	30,418 us	19,286 us	+24.8%	+96.8%
bs=100 sw=10 sl=64	throughput	870 tuples/sec	873 tuples/sec	953.66 tuples/sec	-0.3%	-8.8%
bs=100 sw=10 sl=64	MB/s	0.531 MB/s	0.533 MB/s	0.582 MB/s	-0.4%	-8.8%
bs=100 sw=10 sl=64	p50	108,338 us	108,556 us	105,130 us	-0.2%	+3.1%
bs=100 sw=10 sl=64	p95	171,711 us	154,206 us	111,226 us	+11.4%	+54.4%
bs=100 sw=10 sl=64	p99	171,711 us	154,206 us	121,065 us	+11.4%	+41.8%
bs=1000 sw=10 sl=64	throughput	1,092 tuples/sec	1,119 tuples/sec	984.25 tuples/sec	-2.4%	+10.9%
bs=1000 sw=10 sl=64	MB/s	0.666 MB/s	0.683 MB/s	0.601 MB/s	-2.5%	+10.9%
bs=1000 sw=10 sl=64	p50	903,921 us	893,768 us	1,024,295 us	+1.1%	-11.8%
bs=1000 sw=10 sl=64	p95	1,058,331 us	977,675 us	1,062,710 us	+8.2%	-0.4%
bs=1000 sw=10 sl=64	p99	1,058,331 us	977,675 us	1,095,400 us	+8.2%	-3.4%

Raw CSV

config_idx,batch_size,schema_width,string_len,num_batches,total_ms,total_tuples,total_bytes,tuples_per_sec,mb_per_sec,lat_p50_us,lat_p95_us,lat_p99_us
0,10,10,64,20,535.90,200,128000,373,0.228,24280.08,37959.02,37959.02
1,100,10,64,20,2299.68,2000,1280000,870,0.531,108338.34,171711.33,171711.33
2,1000,10,64,20,18316.44,20000,12800000,1092,0.666,903921.46,1058330.63,1058330.63

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.31%. Comparing base (fb1a5c4) to head (e884e48).
⚠️ Report is 1 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #7446      +/-   ##
============================================
- Coverage     85.33%   85.31%   -0.03%     
+ Complexity     4153     4130      -23     
============================================
  Files          1169     1168       -1     
  Lines         46740    46657      -83     
  Branches       5202     5198       -4     
============================================
- Hits          39887    39806      -81     
+ Misses         5145     5143       -2     
  Partials       1708     1708              

Flag	Coverage Δ		*Carryforward flag
access-control-service	70.00% <ø> (ø)		Carriedforward from fb1a5c4
agent-service	85.50% <ø> (ø)		Carriedforward from fb1a5c4
amber	80.82% <ø> (-0.09%)	⬇️
computing-unit-managing-service	50.72% <ø> (ø)		Carriedforward from fb1a5c4
config-service	65.97% <ø> (ø)		Carriedforward from fb1a5c4
file-service	69.05% <ø> (ø)		Carriedforward from fb1a5c4
frontend	87.85% <ø> (ø)		Carriedforward from fb1a5c4
notebook-migration-service	78.89% <ø> (ø)		Carriedforward from fb1a5c4
pyamber	97.55% <ø> (ø)		Carriedforward from fb1a5c4
workflow-compiling-service	26.31% <ø> (ø)		Carriedforward from fb1a5c4

*This pull request uses carry forward flags. Click here to find out more.

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