ryukobayashi opened a new pull request, #6885:
URL: https://github.com/apache/hive/pull/6885
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### What changes were proposed in this pull request?
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`HiveToSemiJoinRuleSwapInputs` is intended to swap inputs only for `INNER
JOIN` plans that can be converted to a semi-join. However, the rule did not
check the join type before swapping inputs.
This patch adds an explicit `JoinRelType.INNER` check before input swapping.
It also adds:
- Calcite rule-level regression tests for `LEFT JOIN` and `INNER JOIN`
- A qtest reproducing the HIVE-30146 query-result regression
### Why are the changes needed?
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Without this check, a `LEFT JOIN` with an aggregate on the left side could
have its inputs swapped while retaining the `LEFT` join type. The subsequent
semi-join rule processing could then remove the original left input, changing
the preserved-side semantics and producing incorrect results.
For the HIVE-30146 reproduction:
- Before the fix with CBO enabled: `COUNT(*)` returned `4`, and the
right-side values were `1, 1, 3, 4`
- After the fix: `COUNT(*)` returns `3`, and the right-side values are `1,
1, NULL`
### Does this PR introduce _any_ user-facing change?
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Yes. Queries affected by this optimizer rule now return the correct `LEFT
JOIN` results. There are no SQL syntax, API, or configuration changes.
### How was this patch tested?
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- Added and ran `TestHiveSemiJoinRule`
- Confirmed that `LEFT JOIN` plans are not rewritten by the swapped-input
rules
- Confirmed that the existing `INNER JOIN` semi-join conversion still works
- Added and ran `hive_30146_left_join.q` with `TestMiniLlapLocalCliDriver`
- Confirmed that the qtest fails with the expected incorrect results when
the fix is reverted
- Confirmed that the qtest passes after restoring the fix
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