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| <pre>public class <span class="typeNameLabel">Count</span> |
| extends java.lang.Object</pre> |
| <div class="block"><a href="../../../../../org/apache/beam/sdk/transforms/PTransform.html" title="class in org.apache.beam.sdk.transforms"><code>PTransforms</code></a> to count the elements in a <a href="../../../../../org/apache/beam/sdk/values/PCollection.html" title="class in org.apache.beam.sdk.values"><code>PCollection</code></a>. |
| |
| <p><a href="../../../../../org/apache/beam/sdk/transforms/Count.html#perElement--"><code>perElement()</code></a> can be used to count the number of occurrences of each distinct |
| element in the PCollection, <a href="../../../../../org/apache/beam/sdk/transforms/Count.html#perKey--"><code>perKey()</code></a> can be used to count the number of values per |
| key, and <a href="../../../../../org/apache/beam/sdk/transforms/Count.html#globally--"><code>globally()</code></a> can be used to count the total number of elements in a |
| PCollection. |
| |
| <p><a href="../../../../../org/apache/beam/sdk/transforms/Count.html#combineFn--"><code>combineFn()</code></a> can also be used manually, in combination with state and with the <a href="../../../../../org/apache/beam/sdk/transforms/Combine.html" title="class in org.apache.beam.sdk.transforms"><code>Combine</code></a> transform.</div> |
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| <th class="colFirst" scope="col">Modifier and Type</th> |
| <th class="colLast" scope="col">Method and Description</th> |
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| <tr id="i0" class="altColor"> |
| <td class="colFirst"><code>static <T> <a href="../../../../../org/apache/beam/sdk/transforms/Combine.CombineFn.html" title="class in org.apache.beam.sdk.transforms">Combine.CombineFn</a><T,?,java.lang.Long></code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../org/apache/beam/sdk/transforms/Count.html#combineFn--">combineFn</a></span>()</code> |
| <div class="block">Returns a <a href="../../../../../org/apache/beam/sdk/transforms/Combine.CombineFn.html" title="class in org.apache.beam.sdk.transforms"><code>Combine.CombineFn</code></a> that counts the number of its inputs.</div> |
| </td> |
| </tr> |
| <tr id="i1" class="rowColor"> |
| <td class="colFirst"><code>static <T> <a href="../../../../../org/apache/beam/sdk/transforms/PTransform.html" title="class in org.apache.beam.sdk.transforms">PTransform</a><<a href="../../../../../org/apache/beam/sdk/values/PCollection.html" title="class in org.apache.beam.sdk.values">PCollection</a><T>,<a href="../../../../../org/apache/beam/sdk/values/PCollection.html" title="class in org.apache.beam.sdk.values">PCollection</a><java.lang.Long>></code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../org/apache/beam/sdk/transforms/Count.html#globally--">globally</a></span>()</code> |
| <div class="block">Returns a <a href="../../../../../org/apache/beam/sdk/transforms/PTransform.html" title="class in org.apache.beam.sdk.transforms"><code>PTransform</code></a> that counts the number of elements in its input <a href="../../../../../org/apache/beam/sdk/values/PCollection.html" title="class in org.apache.beam.sdk.values"><code>PCollection</code></a>.</div> |
| </td> |
| </tr> |
| <tr id="i2" class="altColor"> |
| <td class="colFirst"><code>static <T> <a href="../../../../../org/apache/beam/sdk/transforms/PTransform.html" title="class in org.apache.beam.sdk.transforms">PTransform</a><<a href="../../../../../org/apache/beam/sdk/values/PCollection.html" title="class in org.apache.beam.sdk.values">PCollection</a><T>,<a href="../../../../../org/apache/beam/sdk/values/PCollection.html" title="class in org.apache.beam.sdk.values">PCollection</a><<a href="../../../../../org/apache/beam/sdk/values/KV.html" title="class in org.apache.beam.sdk.values">KV</a><T,java.lang.Long>>></code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../org/apache/beam/sdk/transforms/Count.html#perElement--">perElement</a></span>()</code> |
| <div class="block">Returns a <a href="../../../../../org/apache/beam/sdk/transforms/PTransform.html" title="class in org.apache.beam.sdk.transforms"><code>PTransform</code></a> that counts the number of occurrences of each element in its input |
| <a href="../../../../../org/apache/beam/sdk/values/PCollection.html" title="class in org.apache.beam.sdk.values"><code>PCollection</code></a>.</div> |
| </td> |
| </tr> |
| <tr id="i3" class="rowColor"> |
| <td class="colFirst"><code>static <K,V> <a href="../../../../../org/apache/beam/sdk/transforms/PTransform.html" title="class in org.apache.beam.sdk.transforms">PTransform</a><<a href="../../../../../org/apache/beam/sdk/values/PCollection.html" title="class in org.apache.beam.sdk.values">PCollection</a><<a href="../../../../../org/apache/beam/sdk/values/KV.html" title="class in org.apache.beam.sdk.values">KV</a><K,V>>,<a href="../../../../../org/apache/beam/sdk/values/PCollection.html" title="class in org.apache.beam.sdk.values">PCollection</a><<a href="../../../../../org/apache/beam/sdk/values/KV.html" title="class in org.apache.beam.sdk.values">KV</a><K,java.lang.Long>>></code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../org/apache/beam/sdk/transforms/Count.html#perKey--">perKey</a></span>()</code> |
| <div class="block">Returns a <a href="../../../../../org/apache/beam/sdk/transforms/PTransform.html" title="class in org.apache.beam.sdk.transforms"><code>PTransform</code></a> that counts the number of elements associated with each key of its |
| input <a href="../../../../../org/apache/beam/sdk/values/PCollection.html" title="class in org.apache.beam.sdk.values"><code>PCollection</code></a>.</div> |
| </td> |
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| <h3>Methods inherited from class java.lang.Object</h3> |
| <code>clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait</code></li> |
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| <h4>combineFn</h4> |
| <pre>public static <T> <a href="../../../../../org/apache/beam/sdk/transforms/Combine.CombineFn.html" title="class in org.apache.beam.sdk.transforms">Combine.CombineFn</a><T,?,java.lang.Long> combineFn()</pre> |
| <div class="block">Returns a <a href="../../../../../org/apache/beam/sdk/transforms/Combine.CombineFn.html" title="class in org.apache.beam.sdk.transforms"><code>Combine.CombineFn</code></a> that counts the number of its inputs.</div> |
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| <h4>globally</h4> |
| <pre>public static <T> <a href="../../../../../org/apache/beam/sdk/transforms/PTransform.html" title="class in org.apache.beam.sdk.transforms">PTransform</a><<a href="../../../../../org/apache/beam/sdk/values/PCollection.html" title="class in org.apache.beam.sdk.values">PCollection</a><T>,<a href="../../../../../org/apache/beam/sdk/values/PCollection.html" title="class in org.apache.beam.sdk.values">PCollection</a><java.lang.Long>> globally()</pre> |
| <div class="block">Returns a <a href="../../../../../org/apache/beam/sdk/transforms/PTransform.html" title="class in org.apache.beam.sdk.transforms"><code>PTransform</code></a> that counts the number of elements in its input <a href="../../../../../org/apache/beam/sdk/values/PCollection.html" title="class in org.apache.beam.sdk.values"><code>PCollection</code></a>. |
| |
| <p>Note: if the input collection uses a windowing strategy other than <a href="../../../../../org/apache/beam/sdk/transforms/windowing/GlobalWindows.html" title="class in org.apache.beam.sdk.transforms.windowing"><code>GlobalWindows</code></a>, |
| use <code>Combine.globally(Count.<T>combineFn()).withoutDefaults()</code> instead.</div> |
| </li> |
| </ul> |
| <a name="perKey--"> |
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| <h4>perKey</h4> |
| <pre>public static <K,V> <a href="../../../../../org/apache/beam/sdk/transforms/PTransform.html" title="class in org.apache.beam.sdk.transforms">PTransform</a><<a href="../../../../../org/apache/beam/sdk/values/PCollection.html" title="class in org.apache.beam.sdk.values">PCollection</a><<a href="../../../../../org/apache/beam/sdk/values/KV.html" title="class in org.apache.beam.sdk.values">KV</a><K,V>>,<a href="../../../../../org/apache/beam/sdk/values/PCollection.html" title="class in org.apache.beam.sdk.values">PCollection</a><<a href="../../../../../org/apache/beam/sdk/values/KV.html" title="class in org.apache.beam.sdk.values">KV</a><K,java.lang.Long>>> perKey()</pre> |
| <div class="block">Returns a <a href="../../../../../org/apache/beam/sdk/transforms/PTransform.html" title="class in org.apache.beam.sdk.transforms"><code>PTransform</code></a> that counts the number of elements associated with each key of its |
| input <a href="../../../../../org/apache/beam/sdk/values/PCollection.html" title="class in org.apache.beam.sdk.values"><code>PCollection</code></a>.</div> |
| </li> |
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| <h4>perElement</h4> |
| <pre>public static <T> <a href="../../../../../org/apache/beam/sdk/transforms/PTransform.html" title="class in org.apache.beam.sdk.transforms">PTransform</a><<a href="../../../../../org/apache/beam/sdk/values/PCollection.html" title="class in org.apache.beam.sdk.values">PCollection</a><T>,<a href="../../../../../org/apache/beam/sdk/values/PCollection.html" title="class in org.apache.beam.sdk.values">PCollection</a><<a href="../../../../../org/apache/beam/sdk/values/KV.html" title="class in org.apache.beam.sdk.values">KV</a><T,java.lang.Long>>> perElement()</pre> |
| <div class="block">Returns a <a href="../../../../../org/apache/beam/sdk/transforms/PTransform.html" title="class in org.apache.beam.sdk.transforms"><code>PTransform</code></a> that counts the number of occurrences of each element in its input |
| <a href="../../../../../org/apache/beam/sdk/values/PCollection.html" title="class in org.apache.beam.sdk.values"><code>PCollection</code></a>. |
| |
| <p>The returned <code>PTransform</code> takes a <code>PCollection<T></code> and returns a <code>PCollection<KV<T, Long>></code> representing a map from each distinct element of the input <code>PCollection</code> to the number of times that element occurs in the input. Each key in the output |
| <code>PCollection</code> is unique. |
| |
| <p>The returned transform compares two values of type <code>T</code> by first encoding each element |
| using the input <code>PCollection</code>'s <code>Coder</code>, then comparing the encoded bytes. Because |
| of this, the input coder must be deterministic. (See <a href="../../../../../org/apache/beam/sdk/coders/Coder.html#verifyDeterministic--"><code>Coder.verifyDeterministic()</code></a> for more detail). Performing the |
| comparison in this manner admits efficient parallel evaluation. |
| |
| <p>By default, the <code>Coder</code> of the keys of the output <code>PCollection</code> is the same as |
| the <code>Coder</code> of the elements of the input <code>PCollection</code>. |
| |
| <p>Example of use: |
| |
| <pre><code> |
| PCollection<String> words = ...; |
| PCollection<KV<String, Long>> wordCounts = |
| words.apply(Count.<String>perElement()); |
| </code></pre></div> |
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