BroadcastNestedLoopJoinExec Binary Physical Operator¶

BroadcastNestedLoopJoinExec is a binary physical operator (with two child <> and <> physical operators) that is <> (and converted to) when JoinSelection physical plan strategy finds a Join.md[Join] logical operator that meets either case:

• canBuildRight join type and right physical operator broadcastable

• canBuildLeft join type and left broadcastable

• non-InnerLike join type

[NOTE]¶

canBuildRight join types are:

• CROSS, INNER, LEFT ANTI, LEFT OUTER, LEFT SEMI or Existence

canBuildLeft join types are:

* CROSS, INNER, RIGHT OUTER¶

val nums = spark.range(2)
val letters = ('a' to 'c').map(_.toString).toDF("letter")
val q = nums.crossJoin(letters)

scala> q.explain
== Physical Plan ==
BroadcastNestedLoopJoin BuildRight, Cross
:- *Range (0, 2, step=1, splits=Some(8))
+- BroadcastExchange IdentityBroadcastMode
   +- LocalTableScan [letter#69]

[[requiredChildDistribution]] .BroadcastNestedLoopJoinExec's Required Child Output Distributions [cols="1m,2,2",options="header",width="100%"] |=== | BuildSide | Left Child | Right Child

| BuildLeft | BroadcastDistribution (uses IdentityBroadcastMode broadcast mode) | UnspecifiedDistribution

| BuildRight | UnspecifiedDistribution | BroadcastDistribution (uses IdentityBroadcastMode broadcast mode) |===

=== [[creating-instance]] Creating BroadcastNestedLoopJoinExec Instance

BroadcastNestedLoopJoinExec takes the following when created:

• [[left]] Left SparkPlan.md[physical operator]
• [[right]] Right SparkPlan.md[physical operator]
• [[buildSide]] BuildSide
• [[joinType]] Join type
• [[condition]] Optional join condition expressions/Expression.md[expressions]

Performance Metrics¶