cloud-fan commented on a change in pull request #30790:
URL: https://github.com/apache/spark/pull/30790#discussion_r544780362
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/expressions.scala
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@@ -523,6 +532,14 @@ object SimplifyConditionals extends Rule[LogicalPlan] with
PredicateHelper {
} else {
e.copy(branches = branches.take(i).map(branch => (branch._1,
elseValue)))
}
+
+ case EqualTo(i @ If(_, trueValue, falseValue), right: Literal)
+ if i.deterministic && isAlwaysFalse(trueValue :: falseValue :: Nil,
right) =>
+ FalseLiteral
+
+ case EqualTo(c @ CaseWhen(branches, elseValue), right: Literal)
Review comment:
A more general idea is to push down `EqualTo`(or other binary
expressions) through If/CaseWhen.
For the example case, `(CASE WHEN id = 1 THEN 'b' WHEN id = 3 THEN 'c' END)
= 'a'`, we go through the following steps
1. CASE WHEN id = 1 THEN 'b' = 'a' WHEN id = 3 THEN 'c' = 'a' END
2. CASE WHEN id = 1 THEN false WHEN id = 3 THEN false END
3. false
Step 3 may need more work in `SimplifyConditionals` to make it possible.
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