Dataset.explain, ExplainCommand and sqlContext.executePlan twice?

[Jacek Laskowski <ja...@japila.pl>]

Hi,

While reviewing explain(extended: Boolean) -
https://github.com/apache/spark/blob/master/sql/core/src/main/scala/org/apache/spark/sql/Dataset.scala#L408
- I've noticed that:

1. It first creates ExplainCommand that does
sqlContext.executePlan(logicalPlan) in run
https://github.com/apache/spark/blob/master/sql/core/src/main/scala/org/apache/spark/sql/execution/command/commands.scala#L247

2. And then calls sqlContext.executePlan(explain)
https://github.com/apache/spark/blob/master/sql/core/src/main/scala/org/apache/spark/sql/Dataset.scala#L410

Why are there two sqlContext.executePlan's? It appears that we calls
the former to execute the latter (?) I'm confused. Please explain :)
I'd appreciate.

Pozdrawiam,
Jacek Laskowski
----
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