github-actions[bot] commented on code in PR #65467:
URL: https://github.com/apache/doris/pull/65467#discussion_r3568715324
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fe/fe-core/src/main/java/org/apache/doris/nereids/hint/LeadingHint.java:
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@@ -474,6 +509,12 @@ public Pair<JoinConstraint, Boolean>
getJoinConstraint(Long joinTableBitmap, Lon
return Pair.of(null, false);
}
+ // The preserved side (minLeftHand) is not yet in the join —
+ // this constraint is not applicable, skip it.
+ if (!LongBitmap.isSubset(joinConstraint.getMinLeftHand(),
joinTableBitmap)) {
+ continue;
Review Comment:
This skip still lets the nullable side of a pending one-sided outer join
absorb unrelated inputs before the preserved side arrives. For example:
```text
CrossJoin
LeftOuterJoin ON a.k = b.k
a
b
c
```
With `leading(b c a)`, the `{b,c}` join reaches this branch because
`minLeftHand={a}` is absent, so it is built as a CROSS join. At the final join,
`{b,c}` vs `{a}` matches the original left outer constraint in reversed form,
consumes `a.k = b.k`, leaves no filters, and the hint can succeed as `(b CROSS
JOIN c) RIGHT OUTER JOIN a`.
That is not equivalent: for unmatched `a` rows the original plan still cross
joins every real `c` row (and returns none if `c` is empty), but the rewritten
right outer join emits a single null-extended row with `c` NULL. Please either
block a pending outer join's nullable side from mixing with unrelated tables
before the preserved side arrives, or require the nullable-side child to remain
exactly the original nullable side when the outer constraint is matched, and
cover both left-outer and right-outer CROSS variants through the real
leading-hint plan path.
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