uros-b commented on code in PR #58119:
URL: https://github.com/apache/spark/pull/58119#discussion_r3865178866
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sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/RewriteWithExpression.scala:
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@@ -66,6 +66,34 @@ object RewriteWithExpression extends Rule[LogicalPlan] {
}
}
+ /**
+ * Rewrites the `With` expressions in a single expression tree by inlining
their common
+ * expressions. Uses `transformUp` to handle nested `With`. Inlining
duplicates a definition at
+ * every reference, so this rejects non-foldable definitions: inlining one
referenced more than
+ * once would evaluate it more than once, breaking `With`'s evaluate-once
contract.
+ *
+ * Does not descend into subquery plans (e.g. `ScalarSubquery`). A caller
whose expression
+ * may contain a subquery must rewrite those plans separately.
+ */
+ def applyForExpression(expression: Expression): Expression =
+ inlineWith(expression, rejectNonFoldableDefs = true)
+
+ // The plan-level rewrite shares this to inline `With` in conditional
branches, which may not be
+ // evaluated and so can't be pulled into a Project; it passes false to allow
non-foldable defs.
+ private def inlineWith(expression: Expression, rejectNonFoldableDefs:
Boolean): Expression = {
+ expression.transformUpWithPruning(_.containsPattern(WITH_EXPRESSION)) {
+ case With(child, defs) =>
+ if (rejectNonFoldableDefs && !defs.forall(_.child.foldable)) {
Review Comment:
CurrentTimestampNanos is foldable but evaluates Instant.now(). Inlining two
references can produce different values, violating With’s evaluate-once
contract.
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