tanelk commented on a change in pull request #29871:
URL: https://github.com/apache/spark/pull/29871#discussion_r495116397
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/CostBasedJoinReorder.scala
##########
@@ -40,30 +40,35 @@ object CostBasedJoinReorder extends Rule[LogicalPlan] with
PredicateHelper {
if (!conf.cboEnabled || !conf.joinReorderEnabled) {
plan
} else {
- val result = plan transformDown {
- // Start reordering with a joinable item, which is an InnerLike join
with conditions.
- // Avoid reordering if a join hint is present.
- case j @ Join(_, _, _: InnerLike, Some(cond), JoinHint.NONE) =>
- reorder(j, j.output)
- case p @ Project(projectList, Join(_, _, _: InnerLike, Some(cond),
JoinHint.NONE))
- if projectList.forall(_.isInstanceOf[Attribute]) =>
- reorder(p, p.output)
- }
+ val result = plan transformDown applyLocally
// After reordering is finished, convert OrderedJoin back to Join.
result transform {
case OrderedJoin(left, right, jt, cond) => Join(left, right, jt, cond,
JoinHint.NONE)
}
}
}
+ private val applyLocally: PartialFunction[LogicalPlan, LogicalPlan] = {
+ // Start reordering with a joinable item, which is an InnerLike join with
conditions.
+ // Avoid reordering if a join hint is present.
+ case j @ Join(_, _, _: InnerLike, Some(cond), JoinHint.NONE) =>
+ reorder(j, j.output)
+ case p @ Project(projectList, Join(_, _, _: InnerLike, Some(cond),
JoinHint.NONE))
+ if projectList.forall(_.isInstanceOf[Attribute]) =>
+ reorder(p, p.output)
+
+ }
+
private def reorder(plan: LogicalPlan, output: Seq[Attribute]): LogicalPlan
= {
val (items, conditions) = extractInnerJoins(plan)
val result =
// Do reordering if the number of items is appropriate and join
conditions exist.
// We also need to check if costs of all items can be evaluated.
if (items.size > 2 && items.size <= conf.joinReorderDPThreshold &&
conditions.nonEmpty &&
items.forall(_.stats.rowCount.isDefined)) {
- JoinReorderDP.search(conf, items, conditions, output)
+ // Transform and sort all the items to guarantee idempotence
+ val transformedItems = items.map(_ transformDown
applyLocally).sortBy(_.semanticHash())
+ JoinReorderDP.search(conf, transformedItems, conditions, output)
Review comment:
This is the most relevant change - previously we reordered the joins
from top to bottom. Now we reorder the joins in the lower groups first and then
reorder the ones on the top.
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