abstract class Broadcast[T] extends Serializable with Logging
A broadcast variable. Broadcast variables allow the programmer to keep a read-only variable cached on each machine rather than shipping a copy of it with tasks. They can be used, for example, to give every node a copy of a large input dataset in an efficient manner. Spark also attempts to distribute broadcast variables using efficient broadcast algorithms to reduce communication cost.
Broadcast variables are created from a variable v
by calling
org.apache.spark.SparkContext#broadcast.
The broadcast variable is a wrapper around v
, and its value can be accessed by calling the
value
method. The interpreter session below shows this:
scala> val broadcastVar = sc.broadcast(Array(1, 2, 3)) broadcastVar: org.apache.spark.broadcast.Broadcast[Array[Int]] = Broadcast(0) scala> broadcastVar.value res0: Array[Int] = Array(1, 2, 3)
After the broadcast variable is created, it should be used instead of the value v
in any
functions run on the cluster so that v
is not shipped to the nodes more than once.
In addition, the object v
should not be modified after it is broadcast in order to ensure
that all nodes get the same value of the broadcast variable (e.g. if the variable is shipped
to a new node later).
- T
Type of the data contained in the broadcast variable.
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Instance Constructors
-
new
Broadcast(id: Long)(implicit arg0: ClassTag[T])
- id
A unique identifier for the broadcast variable.
Abstract Value Members
-
abstract
def
doDestroy(blocking: Boolean): Unit
Actually destroy all data and metadata related to this broadcast variable.
Actually destroy all data and metadata related to this broadcast variable. Implementation of Broadcast class must define their own logic to destroy their own state.
- Attributes
- protected
-
abstract
def
doUnpersist(blocking: Boolean): Unit
Actually unpersist the broadcasted value on the executors.
Actually unpersist the broadcasted value on the executors. Concrete implementations of Broadcast class must define their own logic to unpersist their own data.
- Attributes
- protected
-
abstract
def
getValue(): T
Actually get the broadcasted value.
Actually get the broadcasted value. Concrete implementations of Broadcast class must define their own way to get the value.
- Attributes
- protected
Concrete Value Members
-
final
def
!=(arg0: Any): Boolean
- Definition Classes
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final
def
##(): Int
- Definition Classes
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-
final
def
==(arg0: Any): Boolean
- Definition Classes
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final
def
asInstanceOf[T0]: T0
- Definition Classes
- Any
-
def
assertValid(): Unit
Check if this broadcast is valid.
Check if this broadcast is valid. If not valid, exception is thrown.
- Attributes
- protected
-
def
clone(): AnyRef
- Attributes
- protected[lang]
- Definition Classes
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- @throws( ... ) @native()
-
def
destroy(): Unit
Destroy all data and metadata related to this broadcast variable.
Destroy all data and metadata related to this broadcast variable. Use this with caution; once a broadcast variable has been destroyed, it cannot be used again.
-
final
def
eq(arg0: AnyRef): Boolean
- Definition Classes
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-
def
equals(arg0: Any): Boolean
- Definition Classes
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-
def
finalize(): Unit
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- protected[lang]
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- @throws( classOf[java.lang.Throwable] )
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final
def
getClass(): Class[_]
- Definition Classes
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- @native()
-
def
hashCode(): Int
- Definition Classes
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- Annotations
- @native()
- val id: Long
-
def
initializeLogIfNecessary(isInterpreter: Boolean, silent: Boolean): Boolean
- Attributes
- protected
- Definition Classes
- Logging
-
def
initializeLogIfNecessary(isInterpreter: Boolean): Unit
- Attributes
- protected
- Definition Classes
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final
def
isInstanceOf[T0]: Boolean
- Definition Classes
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-
def
isTraceEnabled(): Boolean
- Attributes
- protected
- Definition Classes
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-
def
log: Logger
- Attributes
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-
def
logDebug(msg: ⇒ String, throwable: Throwable): Unit
- Attributes
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- Definition Classes
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-
def
logDebug(msg: ⇒ String): Unit
- Attributes
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- Definition Classes
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def
logError(msg: ⇒ String, throwable: Throwable): Unit
- Attributes
- protected
- Definition Classes
- Logging
-
def
logError(msg: ⇒ String): Unit
- Attributes
- protected
- Definition Classes
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def
logInfo(msg: ⇒ String, throwable: Throwable): Unit
- Attributes
- protected
- Definition Classes
- Logging
-
def
logInfo(msg: ⇒ String): Unit
- Attributes
- protected
- Definition Classes
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def
logName: String
- Attributes
- protected
- Definition Classes
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-
def
logTrace(msg: ⇒ String, throwable: Throwable): Unit
- Attributes
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- Definition Classes
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-
def
logTrace(msg: ⇒ String): Unit
- Attributes
- protected
- Definition Classes
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-
def
logWarning(msg: ⇒ String, throwable: Throwable): Unit
- Attributes
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-
def
logWarning(msg: ⇒ String): Unit
- Attributes
- protected
- Definition Classes
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final
def
ne(arg0: AnyRef): Boolean
- Definition Classes
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final
def
notify(): Unit
- Definition Classes
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- @native()
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final
def
notifyAll(): Unit
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final
def
synchronized[T0](arg0: ⇒ T0): T0
- Definition Classes
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-
def
toString(): String
- Definition Classes
- Broadcast → AnyRef → Any
-
def
unpersist(blocking: Boolean): Unit
Delete cached copies of this broadcast on the executors.
Delete cached copies of this broadcast on the executors. If the broadcast is used after this is called, it will need to be re-sent to each executor.
- blocking
Whether to block until unpersisting has completed
-
def
unpersist(): Unit
Asynchronously delete cached copies of this broadcast on the executors.
Asynchronously delete cached copies of this broadcast on the executors. If the broadcast is used after this is called, it will need to be re-sent to each executor.
-
def
value: T
Get the broadcasted value.
-
final
def
wait(): Unit
- Definition Classes
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- @throws( ... )
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final
def
wait(arg0: Long, arg1: Int): Unit
- Definition Classes
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- @throws( ... )
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final
def
wait(arg0: Long): Unit
- Definition Classes
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- @throws( ... ) @native()