Skip to content

ResolveJoinStrategyHints Logical Resolution Rule

ResolveJoinStrategyHints is a logical resolution rule to resolve UnresolvedHint logical operators with JoinStrategyHints.

ResolveJoinStrategyHints is a Catalyst rule for transforming logical plans (Rule[LogicalPlan]).

ResolveJoinStrategyHints is part of Hints batch of rules of Logical Analyzer.

Creating Instance

ResolveJoinStrategyHints takes the following to be created:

ResolveJoinStrategyHints is created when:

Hint Names

ResolveJoinStrategyHints takes the hintAliases of the strategies when created.

The hint aliases are the only hints (of UnresolvedHints) that are going to be resolved when ResolveJoinStrategyHints is executed.

Executing Rule

  plan: LogicalPlan): LogicalPlan

apply works with LogicalPlans that contain the UNRESOLVED_HINT tree pattern (that happens to be UnresolvedHints only).

apply traverses the given logical query plan to find UnresolvedHints with names that are among the supported hint names.

For UnresolvedHints with no parameters, apply creates a ResolvedHint (with a HintInfo with the corresponding JoinStrategyHint).

For UnresolvedHints with parameters, apply accepts two types of parameters:

apply applyJoinStrategyHint to create a ResolvedHint.

apply is part of the Rule abstraction.


  plan: LogicalPlan,
  relationsInHint: Set[Seq[String]],
  relationsInHintWithMatch: mutable.HashSet[Seq[String]],
  hintName: String): LogicalPlan




Review the example to use ResolveJoinStrategyHints and other hints

// Use Catalyst DSL to create a logical plan
import org.apache.spark.sql.catalyst.dsl.plans._
val plan = table("t1").join(table("t2")).hint(name = "broadcast", "t1", "table2")
scala> println(plan.numberedTreeString)
00 'UnresolvedHint broadcast, [t1, table2]
01 +- 'Join Inner
02    :- 'UnresolvedRelation [t1], [], false
03    +- 'UnresolvedRelation [t2], [], false
import org.apache.spark.sql.catalyst.analysis.ResolveHints.ResolveJoinStrategyHints
val analyzedPlan = ResolveJoinStrategyHints(plan)
scala> println(analyzedPlan.numberedTreeString)
00 'Join Inner
01 :- 'ResolvedHint (strategy=broadcast)
02 :  +- 'UnresolvedRelation [t1], [], false
03 +- 'UnresolvedRelation [t2], [], false