Github user nongli commented on a diff in the pull request:
https://github.com/apache/spark/pull/11372#discussion_r54990183
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
---
@@ -586,6 +587,52 @@ object NullPropagation extends Rule[LogicalPlan] {
}
/**
+ * Attempts to eliminate reading (unnecessary) NULL values if they are not
required for correctness
+ * by inserting isNotNull filters is the query plan. These filters are
currently inserted beneath
+ * existing Filters and Join operators and are inferred based on their
data constraints.
+ *
+ * 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 {
+ def apply(plan: LogicalPlan): LogicalPlan = plan transform {
+ case filter @ Filter(condition, child: LogicalPlan) =>
+ // We generate a list of additional isNotNull filters from the
operator's existing constraints
+ // but remove those that are either already part of the filter
condition or are part of the
+ // operator's child constraints.
+ val newIsNotNullConstraints =
filter.constraints.filter(_.isInstanceOf[IsNotNull]) --
+ (child.constraints ++ splitConjunctivePredicates(condition))
+ val newCondition = if (newIsNotNullConstraints.nonEmpty) {
+ And(newIsNotNullConstraints.reduce(And), condition)
+ } else {
+ condition
+ }
+ Filter(newCondition, child)
+
+ case join @ Join(left: LogicalPlan, right: LogicalPlan, joinType:
JoinType,
+ condition: Option[Expression]) =>
+ val leftIsNotNullConstraints = join.constraints
+ .filter(_.isInstanceOf[IsNotNull])
+ .filter(_.references.subsetOf(left.outputSet)) -- left.constraints
+ val rightIsNotNullConstraints =
+ join.constraints
+ .filter(_.isInstanceOf[IsNotNull])
+ .filter(_.references.subsetOf(right.outputSet)) --
right.constraints
+ val newLeftChild = if (leftIsNotNullConstraints.nonEmpty) {
+ Filter(leftIsNotNullConstraints.reduce(And), left)
+ } else {
+ left
+ }
+ val newRightChild = if (rightIsNotNullConstraints.nonEmpty) {
+ Filter(rightIsNotNullConstraints.reduce(And), right)
+ } else {
+ right
+ }
+ Join(newLeftChild, newRightChild, joinType, condition)
--- End diff --
same here, would be nice to reuse `join` if it is not changed
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