Question on HashJoin trait

[Chang Chen]

Hi

I am reading Spark SQL codes,  what do streamedPlan and buildPlan
of HashJoin trait for?

protected lazy val (buildPlan, streamedPlan) = buildSide match {
  case BuildLeft => (left, right)
  case BuildRight => (right, left)
}


https://github.com/apache/spark/blob/master/sql/core/src/main/scala/org/apache/spark/sql/execution/joins/HashJoin.scala#L59

Thanks
Chang