Packages

o

org.apache.spark.sql.execution.adaptive

OptimizeSkewedJoin

object OptimizeSkewedJoin extends Rule[SparkPlan] with CustomShuffleReaderRule

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)

Note that, when this rule is enabled, it also coalesces non-skewed partitions like CoalesceShufflePartitions does.

Linear Supertypes
CustomShuffleReaderRule, Rule[SparkPlan], Logging, SQLConfHelper, AnyRef, Any
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Inherited
  1. OptimizeSkewedJoin
  2. CustomShuffleReaderRule
  3. Rule
  4. Logging
  5. SQLConfHelper
  6. AnyRef
  7. Any
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Visibility
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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. final def eq(arg0: AnyRef): Boolean
    Definition Classes
    AnyRef
  9. def equals(arg0: Any): Boolean
    Definition Classes
    AnyRef → Any
  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 hashCode(): Int
    Definition Classes
    AnyRef → Any
    Annotations
    @native()
  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. val ruleName: String
    Definition Classes
    Rule
  34. val supportedShuffleOrigins: Seq[ShuffleOrigin]

    Returns the list of ShuffleOrigins supported by this rule.

    Returns the list of ShuffleOrigins supported by this rule.

    Definition Classes
    OptimizeSkewedJoin → CustomShuffleReaderRule
  35. final def synchronized[T0](arg0: ⇒ T0): T0
    Definition Classes
    AnyRef
  36. def toString(): String
    Definition Classes
    AnyRef → Any
  37. final def wait(): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
  38. final def wait(arg0: Long, arg1: Int): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
  39. final def wait(arg0: Long): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws( ... ) @native()

Inherited from CustomShuffleReaderRule

Inherited from Rule[SparkPlan]

Inherited from Logging

Inherited from SQLConfHelper

Inherited from AnyRef

Inherited from Any

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