davidvrba commented on a change in pull request #27231: [SPARK-28478][SQL]
Remove redundant null checks
URL: https://github.com/apache/spark/pull/27231#discussion_r376236285
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File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/expressions.scala
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@@ -434,6 +434,27 @@ object SimplifyConditionals extends Rule[LogicalPlan]
with PredicateHelper {
case _ => false
}
+ /**
+ * Condition for redundant null check based on intolerant expressions.
+ * @param ifNullExpr expression that takes place if checkedExpr is null
+ * @param ifNotNullExpr expression that takes place if checkedExpr is not
null
+ * @param checkedExpr expression that is checked for null value
+ */
+ private def isRedundantNullCheck(
+ ifNullExpr: Expression,
+ ifNotNullExpr: Expression,
+ checkedExpr: Expression): Boolean = {
+ val isNullIntolerant = ifNotNullExpr.find { x =>
+ !x.isInstanceOf[NullIntolerant] && x.find(e =>
e.semanticEquals(checkedExpr)).nonEmpty
Review comment:
Yeah, `FilterExec.isNullIntolerant(ifNotNullExpr)` is a stronger condition
than we need so in case there is null-tolerant expr inside we need to check if
the null-checked column is in its subtree. Using the logic from
`FilterExec.isNullIntolerant` the function could look like this:
```
def isNullIntolerant(expr: Expression): Boolean = expr match {
case e: NullIntolerant => e.children.forall(isNullIntolerant)
case e if e.find(x => x.semanticEquals(checkedExpr)).isEmpty => true
case _ => false
}
```
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