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c

org.apache.spark.sql.execution.adaptive

OptimizeSkewedJoin

case class OptimizeSkewedJoin(ensureRequirements: EnsureRequirements) extends Rule[SparkPlan] with Product with Serializable

A rule to optimize skewed joins to avoid straggler tasks whose share of data are significantly larger than those of the rest of the tasks.

The general idea is to divide each skew partition into smaller partitions and replicate its matching partition on the other side of the join so that they can run in parallel tasks. Note that when matching partitions from the left side and the right side both have skew, it will become a cartesian product of splits from left and right joining together.

For example, assume the Sort-Merge join has 4 partitions: left: [L1, L2, L3, L4] right: [R1, R2, R3, R4]

Let's say L2, L4 and R3, R4 are skewed, and each of them get split into 2 sub-partitions. This is scheduled to run 4 tasks at the beginning: (L1, R1), (L2, R2), (L3, R3), (L4, R4). This rule expands it to 9 tasks to increase parallelism: (L1, R1), (L2-1, R2), (L2-2, R2), (L3, R3-1), (L3, R3-2), (L4-1, R4-1), (L4-2, R4-1), (L4-1, R4-2), (L4-2, R4-2)

Linear Supertypes
Serializable, Serializable, Product, Equals, Rule[SparkPlan], Logging, SQLConfHelper, AnyRef, Any
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  1. OptimizeSkewedJoin
  2. Serializable
  3. Serializable
  4. Product
  5. Equals
  6. Rule
  7. Logging
  8. SQLConfHelper
  9. AnyRef
  10. Any
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Visibility
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Instance Constructors

  1. new OptimizeSkewedJoin(ensureRequirements: EnsureRequirements)

Value Members

  1. final def !=(arg0: Any): Boolean
    Definition Classes
    AnyRef → Any
  2. final def ##(): Int
    Definition Classes
    AnyRef → Any
  3. final def ==(arg0: Any): Boolean
    Definition Classes
    AnyRef → Any
  4. def apply(plan: SparkPlan): SparkPlan
    Definition Classes
    OptimizeSkewedJoin → Rule
  5. final def asInstanceOf[T0]: T0
    Definition Classes
    Any
  6. def clone(): AnyRef
    Attributes
    protected[lang]
    Definition Classes
    AnyRef
    Annotations
    @throws( ... ) @native()
  7. def conf: SQLConf
    Definition Classes
    SQLConfHelper
  8. val ensureRequirements: EnsureRequirements
  9. final def eq(arg0: AnyRef): Boolean
    Definition Classes
    AnyRef
  10. def finalize(): Unit
    Attributes
    protected[lang]
    Definition Classes
    AnyRef
    Annotations
    @throws( classOf[java.lang.Throwable] )
  11. final def getClass(): Class[_]
    Definition Classes
    AnyRef → Any
    Annotations
    @native()
  12. def getSkewThreshold(medianSize: Long): Long

    A partition is considered as a skewed partition if its size is larger than the median partition size * SKEW_JOIN_SKEWED_PARTITION_FACTOR and also larger than SKEW_JOIN_SKEWED_PARTITION_THRESHOLD.

    A partition is considered as a skewed partition if its size is larger than the median partition size * SKEW_JOIN_SKEWED_PARTITION_FACTOR and also larger than SKEW_JOIN_SKEWED_PARTITION_THRESHOLD. Thus we pick the larger one as the skew threshold.

  13. def initializeLogIfNecessary(isInterpreter: Boolean, silent: Boolean): Boolean
    Attributes
    protected
    Definition Classes
    Logging
  14. def initializeLogIfNecessary(isInterpreter: Boolean): Unit
    Attributes
    protected
    Definition Classes
    Logging
  15. final def isInstanceOf[T0]: Boolean
    Definition Classes
    Any
  16. def isTraceEnabled(): Boolean
    Attributes
    protected
    Definition Classes
    Logging
  17. def log: Logger
    Attributes
    protected
    Definition Classes
    Logging
  18. def logDebug(msg: ⇒ String, throwable: Throwable): Unit
    Attributes
    protected
    Definition Classes
    Logging
  19. def logDebug(msg: ⇒ String): Unit
    Attributes
    protected
    Definition Classes
    Logging
  20. def logError(msg: ⇒ String, throwable: Throwable): Unit
    Attributes
    protected
    Definition Classes
    Logging
  21. def logError(msg: ⇒ String): Unit
    Attributes
    protected
    Definition Classes
    Logging
  22. def logInfo(msg: ⇒ String, throwable: Throwable): Unit
    Attributes
    protected
    Definition Classes
    Logging
  23. def logInfo(msg: ⇒ String): Unit
    Attributes
    protected
    Definition Classes
    Logging
  24. def logName: String
    Attributes
    protected
    Definition Classes
    Logging
  25. def logTrace(msg: ⇒ String, throwable: Throwable): Unit
    Attributes
    protected
    Definition Classes
    Logging
  26. def logTrace(msg: ⇒ String): Unit
    Attributes
    protected
    Definition Classes
    Logging
  27. def logWarning(msg: ⇒ String, throwable: Throwable): Unit
    Attributes
    protected
    Definition Classes
    Logging
  28. def logWarning(msg: ⇒ String): Unit
    Attributes
    protected
    Definition Classes
    Logging
  29. final def ne(arg0: AnyRef): Boolean
    Definition Classes
    AnyRef
  30. final def notify(): Unit
    Definition Classes
    AnyRef
    Annotations
    @native()
  31. final def notifyAll(): Unit
    Definition Classes
    AnyRef
    Annotations
    @native()
  32. def optimizeSkewJoin(plan: SparkPlan): SparkPlan
  33. lazy val ruleId: RuleId
    Attributes
    protected
    Definition Classes
    Rule
  34. val ruleName: String
    Definition Classes
    Rule
  35. final def synchronized[T0](arg0: ⇒ T0): T0
    Definition Classes
    AnyRef
  36. final def wait(): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
  37. final def wait(arg0: Long, arg1: Int): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
  38. final def wait(arg0: Long): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws( ... ) @native()
  39. object ShuffleStage

Inherited from Serializable

Inherited from Serializable

Inherited from Product

Inherited from Equals

Inherited from Rule[SparkPlan]

Inherited from Logging

Inherited from SQLConfHelper

Inherited from AnyRef

Inherited from Any

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