Github user ueshin commented on a diff in the pull request:
https://github.com/apache/spark/pull/13147#discussion_r64981719
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/planning/QueryPlanner.scala
---
@@ -47,17 +55,27 @@ abstract class QueryPlanner[PhysicalPlan <:
TreeNode[PhysicalPlan]] {
/** A list of execution strategies that can be used by the planner */
def strategies: Seq[GenericStrategy[PhysicalPlan]]
- /**
- * Returns a placeholder for a physical plan that executes `plan`. This
placeholder will be
- * filled in automatically by the QueryPlanner using the other execution
strategies that are
- * available.
- */
- protected def planLater(plan: LogicalPlan): PhysicalPlan =
this.plan(plan).next()
-
def plan(plan: LogicalPlan): Iterator[PhysicalPlan] = {
// Obviously a lot to do here still...
- val iter = strategies.view.flatMap(_(plan)).toIterator
+ val iter = strategies.view.flatMap(_(plan)).toIterator.flatMap {
physicalPlan =>
+ val placeholders = collectPlaceholders(physicalPlan)
+
+ (Iterator(physicalPlan) /: placeholders.toIterator) {
+ case (physicalPlans, (placeholder, logicalPlan)) =>
+ val children = this.plan(logicalPlan)
+ physicalPlans.flatMap { physicalPlan =>
+ children.map { child =>
+ physicalPlan.transformUp {
+ case `placeholder` => child
+ }
+ }
+ }
+ }
+ }
+ // TODO: We will need to prune bad plans to prevent from combinatorial
explosion.
--- End diff --
We are not safe now if some strategy returns two or more plans.
Should we take the first plan here for now?
(I will introduce `prune` method and implement it in `SparkPlanner`.)
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