Github user nongli commented on a diff in the pull request:
https://github.com/apache/spark/pull/11665#discussion_r56239773
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
---
@@ -598,50 +598,41 @@ object NullPropagation extends Rule[LogicalPlan] {
}
/**
- * Attempts to eliminate reading (unnecessary) NULL values if they are not
required for correctness
- * by inserting isNotNull filters in the query plan. These filters are
currently inserted beneath
- * existing Filters and Join operators and are inferred based on their
data constraints.
+ * Eliminate reading unnecessary values if they are not required for
correctness (and can help in
+ * optimizing the query) by inserting relevant filters in the query plan
based on an operator's
+ * data constraints. These filters are currently inserted to the existing
conditions in the Filter
+ * operators and on either side of Join operators.
*
* Note: While this optimization is applicable to all types of join, it
primarily benefits Inner and
* LeftSemi joins.
*/
-object NullFiltering extends Rule[LogicalPlan] with PredicateHelper {
+object InferFiltersFromConstraints extends Rule[LogicalPlan] with
PredicateHelper {
+ // We generate a list of additional filters from the operator's existing
constraint but remove
--- End diff --
This comment seems like a clearer version of the first sentence in the
object comment. I'd remove this here and replace the first sentence of the
above comment.
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