apply(plan: SparkPlan): SparkPlanReuseExchange Physical Query Optimization
ReuseExchange is a physical query optimization (aka physical query preparation rule or simply preparation rule) that QueryExecution uses to optimize the physical plan of a structured query by FIXME.
Technically, ReuseExchange is just a Catalyst rule for transforming physical query plans, i.e. Rule[SparkPlan].
ReuseExchange is part of preparations batch of physical query plan rules and is executed when QueryExecution is requested for the optimized physical query plan (i.e. in executedPlan phase of a query execution).
apply Method
|
Note
|
apply is part of Rule Contract to apply a rule to a physical plan.
|
apply finds all Exchange unary operators and…FIXME
apply does nothing and simply returns the input physical plan if spark.sql.exchange.reuse internal configuration property is off (i.e. false).
|
Note
|
spark.sql.exchange.reuse internal configuration property is on (i.e. true) by default.
|