// Use Catalyst DSL to create a logical plan
import org.apache.spark.sql.catalyst.dsl.plans._
val plan = table("t1").hint(name = "COALESCE", 3)
scala> println(plan.numberedTreeString)
00 'UnresolvedHint COALESCE, [3]
01 +- 'UnresolvedRelation `t1`
import org.apache.spark.sql.catalyst.analysis.ResolveHints.ResolveCoalesceHints
val analyzedPlan = ResolveCoalesceHints(plan)
scala> println(analyzedPlan.numberedTreeString)
00 'Repartition 3, false
01 +- 'UnresolvedRelation `t1`ResolveCoalesceHints Logical Resolution Rule — Resolving UnresolvedHint Operators with COALESCE and REPARTITION Hints
ResolveCoalesceHints is a logical resolution rule that the Spark Analyzer uses to resolve UnresolvedHint logical operators with COALESCE or REPARTITION hints (case-insensitive) to ResolvedHint operators.
COALESCE or REPARTITION hints expect a partition number as the only parameter.
Technically, ResolveCoalesceHints is a Catalyst rule for transforming logical plans, i.e. Rule[LogicalPlan].
ResolveCoalesceHints is part of Hints fixed-point batch of rules (that is executed before any other rule).
ResolveCoalesceHints takes no input parameters when created.
Example: Using COALESCE Hint
Example: Using REPARTITION Hint
// Use Catalyst DSL to create a logical plan
import org.apache.spark.sql.catalyst.dsl.plans._
val plan = table("t1").hint(name = "REPARTITION", 3)
scala> println(plan.numberedTreeString)
00 'UnresolvedHint REPARTITION, [3]
01 +- 'UnresolvedRelation `t1`
import org.apache.spark.sql.catalyst.analysis.ResolveHints.ResolveCoalesceHints
val analyzedPlan = ResolveCoalesceHints(plan)
scala> println(analyzedPlan.numberedTreeString)
00 'Repartition 3, true
01 +- 'UnresolvedRelation `t1`Example: Using COALESCE Hint in SQL
val q = sql("SELECT /*+ COALESCE(10) */ * FROM VALUES 1 t(id)")
val plan = q.queryExecution.logical
scala> println(plan.numberedTreeString)
00 'UnresolvedHint COALESCE, [10]
01 +- 'Project [*]
02 +- 'SubqueryAlias `t`
03 +- 'UnresolvedInlineTable [id], [List(1)]
import org.apache.spark.sql.catalyst.analysis.ResolveHints.ResolveCoalesceHints
val analyzedPlan = ResolveCoalesceHints(plan)
scala> println(analyzedPlan.numberedTreeString)
00 'Repartition 10, false
01 +- 'Project [*]
02 +- 'SubqueryAlias `t`
03 +- 'UnresolvedInlineTable [id], [List(1)]