kabo87777 opened a new pull request, #16566:
URL: https://github.com/apache/iotdb/pull/16566
# Fix Non-Deterministic Behavior in AggregationDistributionTest
## Problem
The test `testAggregationWithMultiGroupByLevelNode` was failing
non-deterministically under NonDex with a 40% failure rate due to
order-dependent fragment access.
## Way to Reproduce
```bash
cd iotdb-core/datanode
mvn edu.illinois:nondex-maven-plugin:2.1.1:nondex \
-Dtest=AggregationDistributionTest#testAggregationWithMultiGroupByLevelNode \
-DnondexRuns=5
# Expected: Test fails with certain NonDex seeds (e.g., 1016066, 1098954)
# Failure: AssertionError at line 367 when assertions expect specific
fragment order
```
## Root Cause
The test accessed fragment instances by fixed array indices (`get(0)`,
`get(1)`), assuming they would always appear in a specific order:
```java
// Assumed fragment 0 has descriptor pattern 1
verifyGroupByLevelDescriptor(expectedDescriptorValue,
fragmentInstances.get(0)...);
// Assumed fragment 1 has descriptor pattern 2
verifyGroupByLevelDescriptor(expectedDescriptorValue2,
fragmentInstances.get(1)...);
```
When NonDex shuffled collection iteration order during distributed query
planning, fragment instances appeared in different orders, causing the test to
fail even though the query plan was semantically correct.
## Solution
Made the test **order-independent** by iterating through all fragments and
pattern-matching against expected descriptors instead of accessing by index:
1. **Iterate through all fragments** instead of assuming fixed indices
2. **Pattern-match descriptors** to identify which fragment has which
expected pattern
3. **Verify both patterns exist** regardless of order
```java
boolean foundFirst = false;
boolean foundSecond = false;
for (FragmentInstance instance : fragmentInstances) {
// Extract GroupByLevelNode from fragment
PlanNode childNode = planNodeTree.getChildren().get(0);
if (!(childNode instanceof GroupByLevelNode)) continue;
GroupByLevelNode groupByLevel = (GroupByLevelNode) childNode;
if (matchesExpectedDescriptor(groupByLevel, expectedDescriptorValue1)) {
foundFirst = true;
} else if (matchesExpectedDescriptor(groupByLevel,
expectedDescriptorValue2)) {
foundSecond = true;
}
}
assertTrue("Expected to find fragment with single grouped path descriptor",
foundFirst);
assertTrue("Expected to find fragment with two specific paths descriptor",
foundSecond);
```
Added helper method `matchesExpectedDescriptor()` to check if a
`GroupByLevelNode` matches expected descriptor patterns using set-based
comparison.
---
This PR has:
- [x] been self-reviewed
- [x] been tested with NonDex to verify non-determinism is eliminated
- [x] passed all existing tests
- [x] followed code style guidelines (spotless:apply)
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<hr>
This PR has:
- [ ] been self-reviewed.
- [ ] concurrent read
- [ ] concurrent write
- [ ] concurrent read and write
- [ ] added documentation for new or modified features or behaviors.
- [ ] added Javadocs for most classes and all non-trivial methods.
- [ ] added or updated version, __license__, or notice information
- [ ] added comments explaining the "why" and the intent of the code
wherever would not be obvious
for an unfamiliar reader.
- [ ] added unit tests or modified existing tests to cover new code paths,
ensuring the threshold
for code coverage.
- [ ] added integration tests.
- [ ] been tested in a test IoTDB cluster.
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<hr>
##### Key changed/added classes (or packages if there are too many classes)
in this PR
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