[GitHub] [spark] viirya commented on a change in pull request #29567: [SPARK-32721][SQL] Simplify if clauses with null and boolean

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viirya commented on a change in pull request #29567:
URL: https://github.com/apache/spark/pull/29567#discussion_r479665954



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File path: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/expressions.scala
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@@ -463,6 +463,8 @@ object SimplifyConditionals extends Rule[LogicalPlan] with PredicateHelper {
       case If(Literal(null, _), _, falseValue) => falseValue
       case If(cond, trueValue, falseValue)
         if cond.deterministic && trueValue.semanticEquals(falseValue) => trueValue
+      case If(p, l @ Literal(null, _), FalseLiteral) if !p.nullable => And(p, l)
+      case If(p, l @ Literal(null, _), TrueLiteral) if !p.nullable => Or(Not(p), l)

Review comment:
       Hm, I think for expression rewriting, this won't be much faster. This is like @HyukjinKwon said, should be a rare case. The most likely usage, I think, is to turn a predicate to a form being able to push down to data source.
   
   Adding a rule is too much. As part of existing rule looks more proper.




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