Github user hvanhovell commented on a diff in the pull request:
https://github.com/apache/spark/pull/16046#discussion_r90043228
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/Analyzer.scala
---
@@ -1120,47 +1173,54 @@ class Analyzer(
} else {
a
}
- case w : Window =>
- failOnOuterReference(w)
- failOnNonEqualCorrelatedPredicate(foundNonEqualCorrelatedPred, w)
- w
- case j @ Join(left, _, RightOuter, _) =>
- failOnOuterReference(j)
- failOnOuterReferenceInSubTree(left, "a RIGHT OUTER JOIN")
- j
- // SPARK-18578: Do not allow any correlated predicate
- // in a Full (Outer) Join operator and its descendants
- case j @ Join(_, _, FullOuter, _) =>
- failOnOuterReferenceInSubTree(j, "a FULL OUTER JOIN")
- j
- case j @ Join(_, right, jt, _) if !jt.isInstanceOf[InnerLike] =>
- failOnOuterReference(j)
- failOnOuterReferenceInSubTree(right, "a LEFT (OUTER) JOIN")
+
+ // Join can host correlated expressions.
+ case j @ Join(left, right, joinType, _) =>
+ joinType match {
+ // Inner join, like Filter, can be anywhere.
+ // LeftSemi is a special case of Inner join which returns
+ // only the first matched row to the right table.
+ case _: InnerLike | LeftSemi =>
--- End diff --
I have to admit that have been reviewing a lot of PRs. However I am quite
sure that you cannot define a correlated predicate in the plan on the right
hand side of a `LEFT SEMI`/`early-out join` because we only output the column
of the plan on the left hand side. For example:
```sql
select *
from tbl_a
where exists (select 1
from tbl_b
left semi join( select id
from tbl_c
where tbl_c.id = tbl_a.id) c
on c.id = tbl_b.id)
```
In this example we could not move the correlated predicate ` tbl_c.id =
tbl_a.id` because the Left Semi join does not output `cid`. BTW: In this case
it would actually be OK to convert the Left Semi join into an Inner join.
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