fix: prevent stale tuples after a join - #2532
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Pull request overview
This PR addresses correctness issues in Bavet join/ifExists processing where tuples can be observed “stale” (already retracting/inactive) when read from join storage, leading to invalid filtering evaluation and potentially incorrect intermediate tuple propagation.
Changes:
- Add “from right” guarded insertion/update paths in
AbstractJoinNodeand use them when iterating right tuples from storage during left insert/update. - Update indexed and unindexed join nodes to avoid inserting out-tuples based on retracting right tuples.
- Add regression tests covering the “stale right” scenario across join variants (indexed/unindexed, join/ifExists).
Reviewed changes
Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.
Show a summary per file
| File | Description |
|---|---|
| core/src/test/java/ai/timefold/solver/core/impl/score/stream/common/bi/AbstractBiConstraintStreamTest.java | Adds regression tests reproducing stale-right tuple scenarios for join/ifExists. |
| core/src/main/java/ai/timefold/solver/core/impl/bavet/common/AbstractUnindexedJoinNode.java | Uses guarded insertion when iterating right tuples from list storage during left insert. |
| core/src/main/java/ai/timefold/solver/core/impl/bavet/common/AbstractJoinNode.java | Introduces guarded “from right” insertion and update processing to skip inactive right tuples read from storage. |
| core/src/main/java/ai/timefold/solver/core/impl/bavet/common/AbstractIndexedJoinNode.java | Uses guarded insertion when iterating right tuples from index storage during left propagation. |
| core/src/main/java/ai/timefold/solver/core/impl/bavet/common/AbstractIfExistsNode.java | Skips updating counters from left when the right tuple is already retracting/inactive. |
|
Christopher-Chianelli
approved these changes
Jul 27, 2026
| * Reachable when the right input's node sits in a higher layer than the left input's, | ||
| * which delivers the left's inserts before the right's retracts. | ||
| */ | ||
| protected final void insertOutTupleFilteredFromRight(LeftTuple_ leftTuple, UniTuple<Right_> rightTuple) { |
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TBH not in love with this name; maybe insertOutTupleIfRightActiveFiltered?
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I fixed a left input variant of this a long time ago.
With the help of Claude, I was finally able to reproduce this from the right as well, and fixed it.