[replay #7532] fix(workflow-operator): MAX aggregation checks the wrong empty-group sentinel

[sshiv012]

Replay of apache#7532 for CodeRabbit evaluation.

merge-base 5e41efae2650 head c879f75824d7 stratum scala

Synthetic evaluation PR. Do not merge.

• Fixed maxAgg to detect empty groups with the correct minimum-value sentinel.
• Added regression tests for empty, all-null, type-maximum, and re-aggregated MAX values across supported types.

Contributing author	Lines added	Lines removed
Not specified	103	1

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📝 Walkthrough

Walkthrough

maxAgg now identifies empty results with the type minimum sentinel. Tests cover maximum values, empty and null-only inputs, supported data types, and worker-to-final aggregation.

Changes

MAX aggregation correction

Layer / File(s)	Summary
Correct MAX empty-result detection common/workflow-operator/src/main/scala/org/apache/texera/amber/operator/aggregate/AggregationOperation.scala, common/workflow-operator/src/test/scala/org/apache/texera/amber/operator/aggregate/AggregateOpSpec.scala	maxAgg uses the type minimum sentinel for empty results. Tests cover populated, empty, null-only, and maximum-value inputs for supported types.
Validate partial MAX merging common/workflow-operator/src/test/scala/org/apache/texera/amber/operator/aggregate/AggregationOperationSpec.scala	Tests verify that Int.MaxValue survives partial aggregation and that empty partials merge correctly and finalize to null.

Estimated code review effort: 2 (Simple) | ~10 minutes

Suggested reviewers: aglinxinyuan

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly identifies the MAX aggregation sentinel bug and the workflow-operator fix.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch replay/7532-head

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Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In
`@common/workflow-operator/src/main/scala/org/apache/texera/amber/operator/aggregate/AggregationOperation.scala`:
- Line 240: In the aggregation logic around the partial result handling, stop
using AttributeTypeUtils.minValue(attributeType) as the empty-group sentinel.
Track a separate “value observed” state alongside the aggregate, preserve and
merge that state through local and worker-to-final aggregation, and return null
only when no non-null value was observed. Add tests covering groups whose values
all equal the type minimum.

🪄 Autofix

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: 918ed3e1-bc24-4c9e-9c6b-0dd0e68faee3

📥 Commits

Reviewing files that changed from the base of the PR and between 5e41efa and c879f75.

📒 Files selected for processing (3)

• common/workflow-operator/src/main/scala/org/apache/texera/amber/operator/aggregate/AggregationOperation.scala
• common/workflow-operator/src/test/scala/org/apache/texera/amber/operator/aggregate/AggregateOpSpec.scala
• common/workflow-operator/src/test/scala/org/apache/texera/amber/operator/aggregate/AggregationOperationSpec.scala

[coderabbitai]

🎯 Functional Correctness | 🟠 Major | 🏗️ Heavy lift

Do not use minValue as the empty-group marker.

A non-empty group whose maximum equals AttributeTypeUtils.minValue(attributeType) returns null. For example, MAX(Int.MinValue) keeps the initialized partial because the comparison is not greater than zero. Line 240 then treats that valid result as empty.

Store whether a non-null value was observed separately from the aggregate value. Preserve that state during merge. Add local and worker-to-final tests where every value equals the type minimum.

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In
`@common/workflow-operator/src/main/scala/org/apache/texera/amber/operator/aggregate/AggregationOperation.scala`
at line 240, In the aggregation logic around the partial result handling, stop
using AttributeTypeUtils.minValue(attributeType) as the empty-group sentinel.
Track a separate “value observed” state alongside the aggregate, preserve and
merge that state through local and worker-to-final aggregation, and return null
only when no non-null value was observed. Add tests covering groups whose values
all equal the type minimum.