Github user rxin commented on a diff in the pull request:
https://github.com/apache/spark/pull/7446#discussion_r34964984
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
---
@@ -512,20 +520,52 @@ object SimplifyFilters extends Rule[LogicalPlan] {
*
* This heuristic is valid assuming the expression evaluation cost is
minimal.
*/
-object PushPredicateThroughProject extends Rule[LogicalPlan] {
+object PushPredicateThroughProject extends Rule[LogicalPlan] with
PredicateHelper {
def apply(plan: LogicalPlan): LogicalPlan = plan transform {
case filter @ Filter(condition, project @ Project(fields, grandChild))
=>
- val sourceAliases = fields.collect { case a @ Alias(c, _) =>
- (a.toAttribute: Attribute) -> c
- }.toMap
- project.copy(child = filter.copy(
- replaceAlias(condition, sourceAliases),
- grandChild))
+ // Create a map of Aliases to their values from the child projection.
+ // e.g., 'SELECT a + b AS c, d ...' produces Map(c -> a + b).
+ val aliasMap = AttributeMap(fields.collect {
+ case a: Alias => (a.toAttribute, a.child)
+ })
+
+ // Split the condition into small conditions by `And`, so that we
can push down part of this
+ // condition without nondeterministic expressions.
+ val andConditions = splitConjunctivePredicates(condition)
+ val nondeterministicConditions =
andConditions.filter(hasNondeterministic(_, aliasMap))
+
+ // If there is no nondeterministic conditions, push down the whole
condition.
+ if (nondeterministicConditions.isEmpty) {
+ project.copy(child = Filter(replaceAlias(condition, aliasMap),
grandChild))
+ } else {
+ // If they are all nondeterministic conditions, leave it
un-changed.
+ if (nondeterministicConditions.length == andConditions.length) {
+ filter
+ } else {
+ val deterministicConditions =
andConditions.filterNot(hasNondeterministic(_, aliasMap))
+ // Push down the small conditions without nondeterministic
expressions.
+ val pushedCondition =
deterministicConditions.map(replaceAlias(_, aliasMap)).reduce(And)
+ Filter(nondeterministicConditions.reduce(And),
+ project.copy(child = Filter(pushedCondition, grandChild)))
+ }
+ }
+ }
+
+ private def hasNondeterministic(
+ condition: Expression,
+ sourceAliases: AttributeMap[Expression]) = {
+ condition.exists {
+ case a: Attribute =>
+
sourceAliases.get(a).map(_.exists(!_.deterministic)).getOrElse(false)
+ case _ => false
+ }
--- End diff --
+1 on making deterministic describing the tree rather than the expression.
Might also make sense to have a trait called Nondeterministic that can be
mixin into expressions, so we can easily find out what expressions are not
deterministic.
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