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[SPARK-19355][SQL][Followup] Remove the child.outputOrdering check in global limit #22239

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[SPARK-19355][SQL][Followup] Remove the child.outputOrdering check in global limit #22239

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10 changes: 5 additions & 5 deletions sql/core/src/main/scala/org/apache/spark/sql/execution/limit.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -122,11 +122,11 @@ case class GlobalLimitExec(limit: Int, child: SparkPlan) extends UnaryExecNode {
Nil
}

// During global limit, try to evenly distribute limited rows across data
// partitions. If disabled, scanning data partitions sequentially until reaching limit number.
// Besides, if child output has certain ordering, we can't evenly pick up rows from
// each parititon.
val flatGlobalLimit = sqlContext.conf.limitFlatGlobalLimit && child.outputOrdering == Nil
// This is an optimization to evenly distribute limited rows across all partitions.
// When enabled, Spark goes to take rows at each partition repeatedly until reaching
// limit number. When disabled, Spark takes all rows at first partition, then rows
// at second partition ..., until reaching limit number.
val flatGlobalLimit = sqlContext.conf.limitFlatGlobalLimit

val shuffled = new ShuffledRowRDD(shuffleDependency)

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10 changes: 10 additions & 0 deletions sql/core/src/test/scala/org/apache/spark/sql/execution/TakeOrderedAndProjectSuite.scala
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Expand Up @@ -22,6 +22,7 @@ import scala.util.Random
import org.apache.spark.sql.{DataFrame, Row}
import org.apache.spark.sql.catalyst.dsl.expressions._
import org.apache.spark.sql.catalyst.expressions.Literal
import org.apache.spark.sql.internal.SQLConf
import org.apache.spark.sql.test.SharedSQLContext
import org.apache.spark.sql.types._

Expand All @@ -31,10 +32,19 @@ class TakeOrderedAndProjectSuite extends SparkPlanTest with SharedSQLContext {
private var rand: Random = _
private var seed: Long = 0

private val originalLimitFlatGlobalLimit = SQLConf.get.getConf(SQLConf.LIMIT_FLAT_GLOBAL_LIMIT)

protected override def beforeAll(): Unit = {
super.beforeAll()
seed = System.currentTimeMillis()
rand = new Random(seed)

// Disable the optimization to make Sort-Limit match `TakeOrderedAndProject` semantics.
SQLConf.get.setConf(SQLConf.LIMIT_FLAT_GLOBAL_LIMIT, false)
}

protected override def afterAll() = {
SQLConf.get.setConf(SQLConf.LIMIT_FLAT_GLOBAL_LIMIT, originalLimitFlatGlobalLimit)
}

private def generateRandomInputData(): DataFrame = {
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