stefankandic commented on code in PR #58779:
URL: https://github.com/apache/spark/pull/58779#discussion_r4048657246
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sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/nullExpressions.scala:
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@@ -187,8 +187,17 @@ private case class TypedNullLiteral(child: Expression)
override lazy val replacement: Expression = Literal.create(null,
child.dataType)
- override protected def withNewChildInternal(newChild: Expression):
TypedNullLiteral =
- copy(child = newChild)
+ override protected def withNewChildInternal(newChild: Expression):
Expression =
+ TypedNullLiteral.create(newChild)
+}
+
+private[sql] object TypedNullLiteral {
+ /**
+ * Replaces a resolved child with a typed null marker to avoid 3^n growth in
nested `NullIf`
+ * plans.
+ */
+ def create(child: Expression): TypedNullLiteral = TypedNullLiteral(
+ if (child.resolved) Literal.create(null, child.dataType) else child)
Review Comment:
Fixed by construction now: the null literal is created only after analysis,
using the final value.dataType. It is never visited independently by collation
coercion, so the mismatched-collation state is no longer possible. The
structural invariant is covered in NullExpressionsSuite.
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