Github user nongli commented on a diff in the pull request:
https://github.com/apache/spark/pull/11665#discussion_r56240703
--- 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
+ // those that are either already part of the operator's condition or are
part of the operator's
+ // child constraints.
def apply(plan: LogicalPlan): LogicalPlan = plan transform {
case filter @ Filter(condition, child) =>
- // 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]) --
+ val newFilters = filter.constraints --
(child.constraints ++ splitConjunctivePredicates(condition))
- if (newIsNotNullConstraints.nonEmpty) {
- Filter(And(newIsNotNullConstraints.reduce(And), condition), child)
+ if (newFilters.nonEmpty) {
+ Filter(And(newFilters.reduce(And), condition), child)
} else {
filter
}
- case join @ Join(left, right, joinType, condition) =>
- 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
- }
- if (newLeftChild != left || newRightChild != right) {
- Join(newLeftChild, newRightChild, joinType, condition)
- } else {
- join
+ case join @ Join(left, right, joinType, conditionOpt) =>
+ val additionalConstraints = join.constraints.filter { c =>
+ // Only consider constraints that can be pushed down to either the
left or the right child
+ c.references.subsetOf(left.outputSet) ||
c.references.subsetOf(right.outputSet)} --
--- End diff --
I think this line is really hard to read. Split the
join.constraints.filter{} line from the set difference line and us another
local var
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