Apache Spark SQL 的 physical planner 还没有实现？

[liprais]

看源码找 catalyst 的 cost model 的时候看到了:
/**
* Abstract class for transforming [[plans.logical.LogicalPlan LogicalPlan]]s into physical plans.
* Child classes are responsible for specifying a list of [[Strategy]] objects that each of which
* can return a list of possible physical plan options. If a given strategy is unable to plan all
* of the remaining operators in the tree, it can call [[planLater]], which returns a placeholder
* object that will be filled in using other available strategies.
*
* TODO: RIGHT NOW ONLY ONE PLAN IS RETURNED EVER...
* PLAN SPACE EXPLORATION WILL BE IMPLEMENTED LATER.
*
* @tparam PhysicalPlan The type of physical plan produced by this [[QueryPlanner]]
*/
这跟论文里写的不一样啊?还是我看错地方了?
论文在此: http://dl.acm.org/citation.cfm?id=2742797
源代码在此: https://github.com/apache/spark/blob/master/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/planning/QueryPlanner.scala
简直233