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<div class="subTitle">org.apache.spark.broadcast</div>
<h2 title="Class Broadcast" class="title">Class Broadcast<T></h2>
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<ul class="inheritance">
<li>java.lang.Object</li>
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<li>org.apache.spark.broadcast.Broadcast<T></li>
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<pre>public abstract class <span class="strong">Broadcast<T></span>
extends java.lang.Object
implements java.io.Serializable, <a href="../../../../org/apache/spark/Logging.html" title="interface in org.apache.spark">Logging</a></pre>
<div class="block">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.
<p>
Broadcast variables are created from a variable <code>v</code> by calling
<a href="../../../../org/apache/spark/SparkContext.html#broadcast(T, scala.reflect.ClassTag)"><code>SparkContext.broadcast(T, scala.reflect.ClassTag<T>)</code></a>.
The broadcast variable is a wrapper around <code>v</code>, and its value can be accessed by calling the
<code>value</code> method. The interpreter session below shows this:
<p>
<pre><code>
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)
</code></pre>
<p>
After the broadcast variable is created, it should be used instead of the value <code>v</code> in any
functions run on the cluster so that <code>v</code> is not shipped to the nodes more than once.
In addition, the object <code>v</code> 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).
<p>
param: id A unique identifier for the broadcast variable.</div>
<dl><dt><span class="strong">See Also:</span></dt><dd><a href="../../../../serialized-form.html#org.apache.spark.broadcast.Broadcast">Serialized Form</a></dd></dl>
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<td class="colOne"><code><strong><a href="../../../../org/apache/spark/broadcast/Broadcast.html#Broadcast(long, scala.reflect.ClassTag)">Broadcast</a></strong>(long id,
scala.reflect.ClassTag<<a href="../../../../org/apache/spark/broadcast/Broadcast.html" title="type parameter in Broadcast">T</a>> evidence$1)</code> </td>
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<td class="colFirst"><code>protected void</code></td>
<td class="colLast"><code><strong><a href="../../../../org/apache/spark/broadcast/Broadcast.html#assertValid()">assertValid</a></strong>()</code>
<div class="block">Check if this broadcast is valid.</div>
</td>
</tr>
<tr class="rowColor">
<td class="colFirst"><code>void</code></td>
<td class="colLast"><code><strong><a href="../../../../org/apache/spark/broadcast/Broadcast.html#destroy()">destroy</a></strong>()</code>
<div class="block">Destroy all data and metadata related to this broadcast variable.</div>
</td>
</tr>
<tr class="altColor">
<td class="colFirst"><code>protected abstract void</code></td>
<td class="colLast"><code><strong><a href="../../../../org/apache/spark/broadcast/Broadcast.html#doDestroy(boolean)">doDestroy</a></strong>(boolean blocking)</code>
<div class="block">Actually destroy all data and metadata related to this broadcast variable.</div>
</td>
</tr>
<tr class="rowColor">
<td class="colFirst"><code>protected abstract void</code></td>
<td class="colLast"><code><strong><a href="../../../../org/apache/spark/broadcast/Broadcast.html#doUnpersist(boolean)">doUnpersist</a></strong>(boolean blocking)</code>
<div class="block">Actually unpersist the broadcasted value on the executors.</div>
</td>
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<tr class="altColor">
<td class="colFirst"><code>protected abstract <a href="../../../../org/apache/spark/broadcast/Broadcast.html" title="type parameter in Broadcast">T</a></code></td>
<td class="colLast"><code><strong><a href="../../../../org/apache/spark/broadcast/Broadcast.html#getValue()">getValue</a></strong>()</code>
<div class="block">Actually get the broadcasted value.</div>
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<td class="colFirst"><code>long</code></td>
<td class="colLast"><code><strong><a href="../../../../org/apache/spark/broadcast/Broadcast.html#id()">id</a></strong>()</code> </td>
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<td class="colFirst"><code>java.lang.String</code></td>
<td class="colLast"><code><strong><a href="../../../../org/apache/spark/broadcast/Broadcast.html#toString()">toString</a></strong>()</code> </td>
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<td class="colFirst"><code>void</code></td>
<td class="colLast"><code><strong><a href="../../../../org/apache/spark/broadcast/Broadcast.html#unpersist()">unpersist</a></strong>()</code>
<div class="block">Asynchronously delete cached copies of this broadcast on the executors.</div>
</td>
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<td class="colFirst"><code>void</code></td>
<td class="colLast"><code><strong><a href="../../../../org/apache/spark/broadcast/Broadcast.html#unpersist(boolean)">unpersist</a></strong>(boolean blocking)</code>
<div class="block">Delete cached copies of this broadcast on the executors.</div>
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<tr class="rowColor">
<td class="colFirst"><code><a href="../../../../org/apache/spark/broadcast/Broadcast.html" title="type parameter in Broadcast">T</a></code></td>
<td class="colLast"><code><strong><a href="../../../../org/apache/spark/broadcast/Broadcast.html#value()">value</a></strong>()</code>
<div class="block">Get the broadcasted value.</div>
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<h4>Broadcast</h4>
<pre>public Broadcast(long id,
scala.reflect.ClassTag<<a href="../../../../org/apache/spark/broadcast/Broadcast.html" title="type parameter in Broadcast">T</a>> evidence$1)</pre>
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<pre>public <a href="../../../../org/apache/spark/broadcast/Broadcast.html" title="type parameter in Broadcast">T</a> value()</pre>
<div class="block">Get the broadcasted value.</div>
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<pre>public void unpersist()</pre>
<div class="block">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.</div>
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<pre>public void unpersist(boolean blocking)</pre>
<div class="block">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.</div>
<dl><dt><span class="strong">Parameters:</span></dt><dd><code>blocking</code> - Whether to block until unpersisting has completed</dd></dl>
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<pre>public void destroy()</pre>
<div class="block">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.
This method blocks until destroy has completed</div>
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<pre>protected abstract <a href="../../../../org/apache/spark/broadcast/Broadcast.html" title="type parameter in Broadcast">T</a> getValue()</pre>
<div class="block">Actually get the broadcasted value. Concrete implementations of Broadcast class must
define their own way to get the value.</div>
<dl><dt><span class="strong">Returns:</span></dt><dd>(undocumented)</dd></dl>
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<pre>protected abstract void doUnpersist(boolean blocking)</pre>
<div class="block">Actually unpersist the broadcasted value on the executors. Concrete implementations of
Broadcast class must define their own logic to unpersist their own data.</div>
<dl><dt><span class="strong">Parameters:</span></dt><dd><code>blocking</code> - (undocumented)</dd></dl>
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<pre>protected abstract void doDestroy(boolean blocking)</pre>
<div class="block">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.</div>
<dl><dt><span class="strong">Parameters:</span></dt><dd><code>blocking</code> - (undocumented)</dd></dl>
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<pre>protected void assertValid()</pre>
<div class="block">Check if this broadcast is valid. If not valid, exception is thrown.</div>
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<pre>public java.lang.String toString()</pre>
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