Github user gatorsmile commented on a diff in the pull request:
https://github.com/apache/spark/pull/18652#discussion_r127893543
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/Analyzer.scala
---
@@ -1912,6 +1913,26 @@ class Analyzer(
nondeterToAttr.get(e).map(_.toAttribute).getOrElse(e)
}.copy(child = newChild)
+ case j: Join if j.condition.isDefined &&
!j.condition.get.deterministic =>
+ j match {
+ // We can push down non-deterministic joining keys.
--- End diff --
The major point here is the non-deterministic join condition push-down is
safe only when the results are the exactly same before and after the push down.
After we push it down, basically, it will be evaluated for each row of that
side. Will it be evaluated in the same order and in the same number if we do
not push it down? We can find many different scenarios to break it.
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