github-actions[bot] commented on code in PR #64778:
URL: https://github.com/apache/doris/pull/64778#discussion_r3471398220
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fe/fe-core/src/main/java/org/apache/doris/nereids/rules/analysis/SubExprAnalyzer.java:
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@@ -230,6 +250,26 @@ private void checkRootIsLimit(AnalyzedResult
analyzedResult) {
}
}
+ /**
+ * Check whether the analyzed subquery plan has a top-level scalar
aggregate
+ * (aggregate without GROUP BY). Such an aggregate is guaranteed to return
+ * exactly one row regardless of its input, so EXISTS over it is always
TRUE
+ * and NOT EXISTS is always FALSE. Sorting the single row cannot change
+ * EXISTS semantics, so we also strip leading LogicalSort wrappers.
+ */
+ private boolean hasTopLevelScalarAgg(AnalyzedResult analyzedResult) {
Review Comment:
This helper still misses derived-table alias wrappers. During analysis, a
query like:
```text
WHERE EXISTS (
SELECT * FROM (
SELECT COUNT(*)
FROM (
SELECT c1 FROM t2 WHERE t2.c1 = outer.c1
UNION ALL
SELECT c1 FROM t3 WHERE t3.c1 = outer.c1
) u
) a
)
```
can be reduced to:
```text
LogicalProject(a.c)
LogicalSubQueryAlias(a)
LogicalAggregate(groupBy=[])
LogicalUnion
LogicalFilter(t2.c1 = outer.c1)
LogicalFilter(t3.c1 = outer.c1)
```
`SubExprAnalyzer.analyzeSubquery()` runs during analysis, while
`LogicalSubQueryAliasToLogicalProject` is only applied later in plan
normalization, so this alias can still be present here. Since the loop strips
only `LogicalProject` and `LogicalSort`, `hasTopLevelScalarAgg()` returns false
and line 110 rejects the correlated `LogicalUnion`, even though the scalar
aggregate still guarantees one row and `EXISTS`/`NOT EXISTS` should fold to
TRUE/FALSE. Please also treat `LogicalSubQueryAlias` as a transparent wrapper
here, or share the existing top-level scalar aggregate helper that already
allows it, and add a regression for this derived-table shape.
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