Github user mgaido91 commented on a diff in the pull request:
https://github.com/apache/spark/pull/19729#discussion_r150501441
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/arithmetic.scala
---
@@ -604,6 +604,8 @@ case class Least(children: Seq[Expression]) extends
Expression {
val evalChildren = children.map(_.genCode(ctx))
val first = evalChildren(0)
--- End diff --
before using `ev.value`, `ev.isNull` is checked
(https://github.com/kiszk/spark/blob/bc3f0a43956a1e46928f0269d1d8d0aad9ee02b1/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/arithmetic.scala#L612).
So in case of all children with `-2`, the first one will see that `ev.isNull`
is `true` and then it will set it to `false` and assign `-2` to `ev.value`.
Thus the initial value assigned to `ev.value` is irrelevant, since `ev.isNull`
is `true` and as far as `ev.isNull` is `true`, what `ev.value` contains doesn't
matter.
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