bhollis-dbx commented on code in PR #58800:
URL: https://github.com/apache/spark/pull/58800#discussion_r4075567492
##########
sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/trees/TreeNodeSuite.scala:
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@@ -180,6 +181,76 @@ class TreeNodeSuite extends SparkFunSuite with SQLHelper {
assert(actual === expect)
}
+ test("mapChildren returns the original node when all children are fast
equal") {
+ val expression = Coalesce(Seq(Literal(1), Literal(2)))
+ val visited = new ArrayBuffer[Int]()
+ val result = expression.mapChildren {
+ case literal @ Literal(value: Int, _) =>
+ visited += value
+ literal
+ case other => other
+ }
+
+ assert(result eq expression)
+ assert(visited == Seq(1, 2))
+ val leaf = Dummy(None)
+ assert(leaf.mapChildren(identity) eq leaf)
+ }
+
+ test("mapChildren returns the original node when every child is equal but a
distinct copy") {
+ val expression = Coalesce(Seq(Literal(1), Literal(2)))
+ // Return a fresh, structurally-equal (not reference-equal) copy for
*every* child: this
+ // fills `equalCopies` yet must still return `this`, since no child
materially changes.
+ val result = expression.mapChildren {
+ case Literal(value: Int, dt) => Literal(value, dt)
+ case other => other
+ }
+ assert(result eq expression)
+ }
+
+ test("mapChildren retains an equal replacement when another child changes") {
+ val tag = TreeNodeTag[String]("equal-copy")
+ val expression = Coalesce(Seq(Literal(1), Literal(2)))
+ val equalCopy = Literal(1)
+ equalCopy.setTagValue(tag, "retained")
+
+ val result = expression.mapChildren {
+ case Literal(1, _) => equalCopy
+ case Literal(2, _) => Literal(3)
+ case other => other
+ }
+
+ assert(result.children.head eq equalCopy)
+ assert(result.children.head.getTagValue(tag).contains("retained"))
+ assert(result.children(1) == Literal(3))
+ }
+
+ test("mapChildren retains non-adjacent equal replacements when a later child
changes") {
+ val c0 = Literal(10)
+ val c1 = Literal(11)
+ val c2 = Literal(12)
+ val c3 = Literal(13)
+ val expression = Coalesce(Seq(c0, c1, c2, c3))
+ val copy0 = Literal(10)
+ val copy2 = Literal(12)
+
+ // Equal-but-distinct copies at non-adjacent indices 0 and 2, an unchanged
same instance at 1,
+ // and a material change at 3. Exercises the replay loop's index
bookkeeping across a gap.
Review Comment:
The test now keeps c0 reference-equal before copy1, exercising prefix
backfill. It also asserts all five child identities/order and retains a later
material change at c4.
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