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| <pre>public class <span class="typeNameLabel">View</span> |
| extends java.lang.Object</pre> |
| <div class="block">Transforms for creating <a href="../../../../../org/apache/beam/sdk/values/PCollectionView.html" title="interface in org.apache.beam.sdk.values"><code>PCollectionViews</code></a> from <a href="../../../../../org/apache/beam/sdk/values/PCollection.html" title="class in org.apache.beam.sdk.values"><code>PCollections</code></a> (to read them as side inputs). |
| |
| <p>While a <a href="../../../../../org/apache/beam/sdk/values/PCollection.html" title="class in org.apache.beam.sdk.values"><code>PCollection<ElemT></code></a> has many values of type <code>ElemT</code> per |
| window, a <a href="../../../../../org/apache/beam/sdk/values/PCollectionView.html" title="interface in org.apache.beam.sdk.values"><code>PCollectionView<ViewT></code></a> has a single value of type <code>ViewT</code> for each window. It can be thought of as a mapping from windows to values of type <code>ViewT</code>. The transforms here represent ways of converting the <code>ElemT</code> values in a window |
| into a <code>ViewT</code> for that window. |
| |
| <p>When a <a href="../../../../../org/apache/beam/sdk/transforms/ParDo.html" title="class in org.apache.beam.sdk.transforms"><code>ParDo</code></a> tranform is processing a main input element in a window <code>w</code> and a |
| <a href="../../../../../org/apache/beam/sdk/values/PCollectionView.html" title="interface in org.apache.beam.sdk.values"><code>PCollectionView</code></a> is read via <a href="../../../../../org/apache/beam/sdk/transforms/DoFn.ProcessContext.html#sideInput-org.apache.beam.sdk.values.PCollectionView-"><code>DoFn.ProcessContext.sideInput(org.apache.beam.sdk.values.PCollectionView<T>)</code></a>, the value of the view |
| for <code>w</code> is returned. |
| |
| <p>The SDK supports viewing a <a href="../../../../../org/apache/beam/sdk/values/PCollection.html" title="class in org.apache.beam.sdk.values"><code>PCollection</code></a>, per window, as a single value, a <code>List</code>, |
| an <code>Iterable</code>, a <code>Map</code>, or a multimap (iterable-valued <code>Map</code>). |
| |
| <p>For a <a href="../../../../../org/apache/beam/sdk/values/PCollection.html" title="class in org.apache.beam.sdk.values"><code>PCollection</code></a> that contains a single value of type <code>T</code> per window, such as |
| the output of <a href="../../../../../org/apache/beam/sdk/transforms/Combine.html#globally-org.apache.beam.sdk.transforms.SerializableFunction-"><code>Combine.globally(org.apache.beam.sdk.transforms.SerializableFunction<java.lang.Iterable<V>, V>)</code></a>, use <a href="../../../../../org/apache/beam/sdk/transforms/View.html#asSingleton--"><code>asSingleton()</code></a> to prepare it for use as a |
| side input: |
| |
| <pre><code> |
| PCollectionView<T> output = someOtherPCollection |
| .apply(Combine.globally(...)) |
| .apply(View.<T>asSingleton()); |
| </code></pre> |
| |
| <p>For a small <a href="../../../../../org/apache/beam/sdk/values/PCollection.html" title="class in org.apache.beam.sdk.values"><code>PCollection</code></a> with windows that can fit entirely in memory, use <a href="../../../../../org/apache/beam/sdk/transforms/View.html#asList--"><code>asList()</code></a> to prepare it for use as a <code>List</code>. When read as a side input, the entire |
| list for a window will be cached in memory. |
| |
| <pre><code> |
| PCollectionView<List<T>> output = |
| smallPCollection.apply(View.<T>asList()); |
| </code></pre> |
| |
| <p>If a <a href="../../../../../org/apache/beam/sdk/values/PCollection.html" title="class in org.apache.beam.sdk.values"><code>PCollection</code></a> of <code>KV<K, V></code> is known to have a single value per window for |
| each key, then use <a href="../../../../../org/apache/beam/sdk/transforms/View.html#asMap--"><code>asMap()</code></a> to view it as a <code>Map<K, V></code>: |
| |
| <pre><code> |
| PCollectionView<Map<K, V> output = |
| somePCollection.apply(View.<K, V>asMap()); |
| </code></pre> |
| |
| <p>Otherwise, to access a <a href="../../../../../org/apache/beam/sdk/values/PCollection.html" title="class in org.apache.beam.sdk.values"><code>PCollection</code></a> of <code>KV<K, V></code> as a <code>Map<K, |
| Iterable<V>></code> side input, use <a href="../../../../../org/apache/beam/sdk/transforms/View.html#asMultimap--"><code>asMultimap()</code></a>: |
| |
| <pre><code> |
| PCollectionView<Map<K, Iterable<V>> output = |
| somePCollection.apply(View.<K, Iterable<V>>asMultimap()); |
| </code></pre> |
| |
| <p>To iterate over an entire window of a <a href="../../../../../org/apache/beam/sdk/values/PCollection.html" title="class in org.apache.beam.sdk.values"><code>PCollection</code></a> via side input, use <a href="../../../../../org/apache/beam/sdk/transforms/View.html#asIterable--"><code>asIterable()</code></a>: |
| |
| <pre><code> |
| PCollectionView<Iterable<T>> output = |
| somePCollection.apply(View.<T>asIterable()); |
| </code></pre> |
| |
| <p>Both <a href="../../../../../org/apache/beam/sdk/transforms/View.html#asMultimap--"><code>asMultimap()</code></a> and <a href="../../../../../org/apache/beam/sdk/transforms/View.html#asMap--"><code>asMap()</code></a> are useful for implementing lookup |
| based "joins" with the main input, when the side input is small enough to fit into memory. |
| |
| <p>For example, if you represent a page on a website via some <code>Page</code> object and have some |
| type <code>UrlVisits</code> logging that a URL was visited, you could convert these to more fully |
| structured <code>PageVisit</code> objects using a side input, something like the following: |
| |
| <pre><code> |
| PCollection<Page> pages = ... // pages fit into memory |
| PCollection<UrlVisit> urlVisits = ... // very large collection |
| final PCollectionView<Map<URL, Page>> urlToPageView = pages |
| .apply(WithKeys.of( ... )) // extract the URL from the page |
| .apply(View.<URL, Page>asMap()); |
| |
| PCollection<PageVisit> pageVisits = urlVisits |
| .apply(ParDo.withSideInputs(urlToPageView) |
| .of(new DoFn<UrlVisit, PageVisit>() </code>{ |
| <code> @Override |
| void processElement(ProcessContext context) { |
| UrlVisit urlVisit = context.element(); |
| Map<URL, Page> urlToPage = context.sideInput(urlToPageView); |
| Page page = urlToPage.get(urlVisit.getUrl()); |
| c.output(new PageVisit(page, urlVisit.getVisitData())); |
| } |
| </code>})); |
| </pre> |
| |
| <p>See <a href="../../../../../org/apache/beam/sdk/transforms/ParDo.SingleOutput.html#withSideInputs-org.apache.beam.sdk.values.PCollectionView...-"><code>ParDo.SingleOutput.withSideInputs(org.apache.beam.sdk.values.PCollectionView<?>...)</code></a> for details on how to access this variable |
| inside a <a href="../../../../../org/apache/beam/sdk/transforms/ParDo.html" title="class in org.apache.beam.sdk.transforms"><code>ParDo</code></a> over another <a href="../../../../../org/apache/beam/sdk/values/PCollection.html" title="class in org.apache.beam.sdk.values"><code>PCollection</code></a>.</div> |
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| </ul> |
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| <caption><span>Nested Classes</span><span class="tabEnd"> </span></caption> |
| <tr> |
| <th class="colFirst" scope="col">Modifier and Type</th> |
| <th class="colLast" scope="col">Class and Description</th> |
| </tr> |
| <tr class="altColor"> |
| <td class="colFirst"><code>static class </code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../org/apache/beam/sdk/transforms/View.AsIterable.html" title="class in org.apache.beam.sdk.transforms">View.AsIterable</a><<a href="../../../../../org/apache/beam/sdk/transforms/View.AsIterable.html" title="type parameter in View.AsIterable">T</a>></span></code> |
| <div class="block"><b><i>For internal use only; no backwards-compatibility guarantees.</i></b></div> |
| </td> |
| </tr> |
| <tr class="rowColor"> |
| <td class="colFirst"><code>static class </code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../org/apache/beam/sdk/transforms/View.AsList.html" title="class in org.apache.beam.sdk.transforms">View.AsList</a><<a href="../../../../../org/apache/beam/sdk/transforms/View.AsList.html" title="type parameter in View.AsList">T</a>></span></code> |
| <div class="block"><b><i>For internal use only; no backwards-compatibility guarantees.</i></b></div> |
| </td> |
| </tr> |
| <tr class="altColor"> |
| <td class="colFirst"><code>static class </code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../org/apache/beam/sdk/transforms/View.AsMap.html" title="class in org.apache.beam.sdk.transforms">View.AsMap</a><<a href="../../../../../org/apache/beam/sdk/transforms/View.AsMap.html" title="type parameter in View.AsMap">K</a>,<a href="../../../../../org/apache/beam/sdk/transforms/View.AsMap.html" title="type parameter in View.AsMap">V</a>></span></code> |
| <div class="block"><b><i>For internal use only; no backwards-compatibility guarantees.</i></b></div> |
| </td> |
| </tr> |
| <tr class="rowColor"> |
| <td class="colFirst"><code>static class </code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../org/apache/beam/sdk/transforms/View.AsMultimap.html" title="class in org.apache.beam.sdk.transforms">View.AsMultimap</a><<a href="../../../../../org/apache/beam/sdk/transforms/View.AsMultimap.html" title="type parameter in View.AsMultimap">K</a>,<a href="../../../../../org/apache/beam/sdk/transforms/View.AsMultimap.html" title="type parameter in View.AsMultimap">V</a>></span></code> |
| <div class="block"><b><i>For internal use only; no backwards-compatibility guarantees.</i></b></div> |
| </td> |
| </tr> |
| <tr class="altColor"> |
| <td class="colFirst"><code>static class </code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../org/apache/beam/sdk/transforms/View.AsSingleton.html" title="class in org.apache.beam.sdk.transforms">View.AsSingleton</a><<a href="../../../../../org/apache/beam/sdk/transforms/View.AsSingleton.html" title="type parameter in View.AsSingleton">T</a>></span></code> |
| <div class="block"><b><i>For internal use only; no backwards-compatibility guarantees.</i></b></div> |
| </td> |
| </tr> |
| <tr class="rowColor"> |
| <td class="colFirst"><code>static class </code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../org/apache/beam/sdk/transforms/View.CreatePCollectionView.html" title="class in org.apache.beam.sdk.transforms">View.CreatePCollectionView</a><<a href="../../../../../org/apache/beam/sdk/transforms/View.CreatePCollectionView.html" title="type parameter in View.CreatePCollectionView">ElemT</a>,<a href="../../../../../org/apache/beam/sdk/transforms/View.CreatePCollectionView.html" title="type parameter in View.CreatePCollectionView">ViewT</a>></span></code> |
| <div class="block"><b><i>For internal use only; no backwards-compatibility guarantees.</i></b></div> |
| </td> |
| </tr> |
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| <tr id="i0" class="altColor"> |
| <td class="colFirst"><code>static <T> <a href="../../../../../org/apache/beam/sdk/transforms/View.AsIterable.html" title="class in org.apache.beam.sdk.transforms">View.AsIterable</a><T></code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../org/apache/beam/sdk/transforms/View.html#asIterable--">asIterable</a></span>()</code> |
| <div class="block">Returns a <a href="../../../../../org/apache/beam/sdk/transforms/View.AsIterable.html" title="class in org.apache.beam.sdk.transforms"><code>View.AsIterable</code></a> transform that takes a <a href="../../../../../org/apache/beam/sdk/values/PCollection.html" title="class in org.apache.beam.sdk.values"><code>PCollection</code></a> as input and |
| produces a <a href="../../../../../org/apache/beam/sdk/values/PCollectionView.html" title="interface in org.apache.beam.sdk.values"><code>PCollectionView</code></a> mapping each window to an <code>Iterable</code> of the values in |
| that window.</div> |
| </td> |
| </tr> |
| <tr id="i1" class="rowColor"> |
| <td class="colFirst"><code>static <T> <a href="../../../../../org/apache/beam/sdk/transforms/View.AsList.html" title="class in org.apache.beam.sdk.transforms">View.AsList</a><T></code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../org/apache/beam/sdk/transforms/View.html#asList--">asList</a></span>()</code> |
| <div class="block">Returns a <a href="../../../../../org/apache/beam/sdk/transforms/View.AsList.html" title="class in org.apache.beam.sdk.transforms"><code>View.AsList</code></a> transform that takes a <a href="../../../../../org/apache/beam/sdk/values/PCollection.html" title="class in org.apache.beam.sdk.values"><code>PCollection</code></a> and returns a <a href="../../../../../org/apache/beam/sdk/values/PCollectionView.html" title="interface in org.apache.beam.sdk.values"><code>PCollectionView</code></a> mapping each window to a <code>List</code> containing all of the elements in the |
| window.</div> |
| </td> |
| </tr> |
| <tr id="i2" class="altColor"> |
| <td class="colFirst"><code>static <K,V> <a href="../../../../../org/apache/beam/sdk/transforms/View.AsMap.html" title="class in org.apache.beam.sdk.transforms">View.AsMap</a><K,V></code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../org/apache/beam/sdk/transforms/View.html#asMap--">asMap</a></span>()</code> |
| <div class="block">Returns a <a href="../../../../../org/apache/beam/sdk/transforms/View.AsMap.html" title="class in org.apache.beam.sdk.transforms"><code>View.AsMap</code></a> transform that takes a <a href="../../../../../org/apache/beam/sdk/values/PCollection.html" title="class in org.apache.beam.sdk.values"><code>PCollection<KV<K, |
| V>></code></a> as input and produces a <a href="../../../../../org/apache/beam/sdk/values/PCollectionView.html" title="interface in org.apache.beam.sdk.values"><code>PCollectionView</code></a> mapping each window to a <code>Map<K, V></code>.</div> |
| </td> |
| </tr> |
| <tr id="i3" class="rowColor"> |
| <td class="colFirst"><code>static <K,V> <a href="../../../../../org/apache/beam/sdk/transforms/View.AsMultimap.html" title="class in org.apache.beam.sdk.transforms">View.AsMultimap</a><K,V></code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../org/apache/beam/sdk/transforms/View.html#asMultimap--">asMultimap</a></span>()</code> |
| <div class="block">Returns a <a href="../../../../../org/apache/beam/sdk/transforms/View.AsMultimap.html" title="class in org.apache.beam.sdk.transforms"><code>View.AsMultimap</code></a> transform that takes a <a href="../../../../../org/apache/beam/sdk/values/PCollection.html" title="class in org.apache.beam.sdk.values"><code>PCollection<KV<K, V>></code></a> as input and produces a <a href="../../../../../org/apache/beam/sdk/values/PCollectionView.html" title="interface in org.apache.beam.sdk.values"><code>PCollectionView</code></a> mapping each |
| window to its contents as a <code>Map<K, Iterable<V>></code> for use as a side |
| input.</div> |
| </td> |
| </tr> |
| <tr id="i4" class="altColor"> |
| <td class="colFirst"><code>static <T> <a href="../../../../../org/apache/beam/sdk/transforms/View.AsSingleton.html" title="class in org.apache.beam.sdk.transforms">View.AsSingleton</a><T></code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../org/apache/beam/sdk/transforms/View.html#asSingleton--">asSingleton</a></span>()</code> |
| <div class="block">Returns a <a href="../../../../../org/apache/beam/sdk/transforms/View.AsSingleton.html" title="class in org.apache.beam.sdk.transforms"><code>View.AsSingleton</code></a> transform that takes a <a href="../../../../../org/apache/beam/sdk/values/PCollection.html" title="class in org.apache.beam.sdk.values"><code>PCollection</code></a> with a single value |
| per window as input and produces a <a href="../../../../../org/apache/beam/sdk/values/PCollectionView.html" title="interface in org.apache.beam.sdk.values"><code>PCollectionView</code></a> that returns the value in the main |
| input window when read as a side input.</div> |
| </td> |
| </tr> |
| </table> |
| <ul class="blockList"> |
| <li class="blockList"><a name="methods.inherited.from.class.java.lang.Object"> |
| <!-- --> |
| </a> |
| <h3>Methods inherited from class java.lang.Object</h3> |
| <code>clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait</code></li> |
| </ul> |
| </li> |
| </ul> |
| </li> |
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| <a name="asSingleton--"> |
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| </a> |
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| <h4>asSingleton</h4> |
| <pre>public static <T> <a href="../../../../../org/apache/beam/sdk/transforms/View.AsSingleton.html" title="class in org.apache.beam.sdk.transforms">View.AsSingleton</a><T> asSingleton()</pre> |
| <div class="block">Returns a <a href="../../../../../org/apache/beam/sdk/transforms/View.AsSingleton.html" title="class in org.apache.beam.sdk.transforms"><code>View.AsSingleton</code></a> transform that takes a <a href="../../../../../org/apache/beam/sdk/values/PCollection.html" title="class in org.apache.beam.sdk.values"><code>PCollection</code></a> with a single value |
| per window as input and produces a <a href="../../../../../org/apache/beam/sdk/values/PCollectionView.html" title="interface in org.apache.beam.sdk.values"><code>PCollectionView</code></a> that returns the value in the main |
| input window when read as a side input. |
| |
| <pre><code> |
| PCollection<InputT> input = ... |
| CombineFn<InputT, OutputT> yourCombineFn = ... |
| PCollectionView<OutputT> output = input |
| .apply(Combine.globally(yourCombineFn)) |
| .apply(View.<OutputT>asSingleton()); |
| </code></pre> |
| |
| <p>If the input <a href="../../../../../org/apache/beam/sdk/values/PCollection.html" title="class in org.apache.beam.sdk.values"><code>PCollection</code></a> is empty, throws <code>NoSuchElementException</code> |
| in the consuming <a href="../../../../../org/apache/beam/sdk/transforms/DoFn.html" title="class in org.apache.beam.sdk.transforms"><code>DoFn</code></a>. |
| |
| <p>If the input <a href="../../../../../org/apache/beam/sdk/values/PCollection.html" title="class in org.apache.beam.sdk.values"><code>PCollection</code></a> contains more than one element, throws <code>IllegalArgumentException</code> in the consuming <a href="../../../../../org/apache/beam/sdk/transforms/DoFn.html" title="class in org.apache.beam.sdk.transforms"><code>DoFn</code></a>.</div> |
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| <h4>asList</h4> |
| <pre>public static <T> <a href="../../../../../org/apache/beam/sdk/transforms/View.AsList.html" title="class in org.apache.beam.sdk.transforms">View.AsList</a><T> asList()</pre> |
| <div class="block">Returns a <a href="../../../../../org/apache/beam/sdk/transforms/View.AsList.html" title="class in org.apache.beam.sdk.transforms"><code>View.AsList</code></a> transform that takes a <a href="../../../../../org/apache/beam/sdk/values/PCollection.html" title="class in org.apache.beam.sdk.values"><code>PCollection</code></a> and returns a <a href="../../../../../org/apache/beam/sdk/values/PCollectionView.html" title="interface in org.apache.beam.sdk.values"><code>PCollectionView</code></a> mapping each window to a <code>List</code> containing all of the elements in the |
| window. |
| |
| <p>Unlike with <a href="../../../../../org/apache/beam/sdk/transforms/View.html#asIterable--"><code>asIterable()</code></a>, the resulting list is required to fit in memory.</div> |
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| <h4>asIterable</h4> |
| <pre>public static <T> <a href="../../../../../org/apache/beam/sdk/transforms/View.AsIterable.html" title="class in org.apache.beam.sdk.transforms">View.AsIterable</a><T> asIterable()</pre> |
| <div class="block">Returns a <a href="../../../../../org/apache/beam/sdk/transforms/View.AsIterable.html" title="class in org.apache.beam.sdk.transforms"><code>View.AsIterable</code></a> transform that takes a <a href="../../../../../org/apache/beam/sdk/values/PCollection.html" title="class in org.apache.beam.sdk.values"><code>PCollection</code></a> as input and |
| produces a <a href="../../../../../org/apache/beam/sdk/values/PCollectionView.html" title="interface in org.apache.beam.sdk.values"><code>PCollectionView</code></a> mapping each window to an <code>Iterable</code> of the values in |
| that window. |
| |
| <p>The values of the <code>Iterable</code> for a window are not required to fit in memory, but they |
| may also not be effectively cached. If it is known that every window fits in memory, and |
| stronger caching is desired, use <a href="../../../../../org/apache/beam/sdk/transforms/View.html#asList--"><code>asList()</code></a>.</div> |
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| <pre>public static <K,V> <a href="../../../../../org/apache/beam/sdk/transforms/View.AsMap.html" title="class in org.apache.beam.sdk.transforms">View.AsMap</a><K,V> asMap()</pre> |
| <div class="block">Returns a <a href="../../../../../org/apache/beam/sdk/transforms/View.AsMap.html" title="class in org.apache.beam.sdk.transforms"><code>View.AsMap</code></a> transform that takes a <a href="../../../../../org/apache/beam/sdk/values/PCollection.html" title="class in org.apache.beam.sdk.values"><code>PCollection<KV<K, |
| V>></code></a> as input and produces a <a href="../../../../../org/apache/beam/sdk/values/PCollectionView.html" title="interface in org.apache.beam.sdk.values"><code>PCollectionView</code></a> mapping each window to a <code>Map<K, V></code>. It is required that each key of the input be associated with a single value, |
| per window. If this is not the case, precede this view with <code>Combine.perKey</code>, as in the |
| example below, or alternatively use <a href="../../../../../org/apache/beam/sdk/transforms/View.html#asMultimap--"><code>asMultimap()</code></a>. |
| |
| <pre><code> |
| PCollection<KV<K, V>> input = ... |
| CombineFn<V, OutputT> yourCombineFn = ... |
| PCollectionView<Map<K, OutputT>> output = input |
| .apply(Combine.perKey(yourCombineFn)) |
| .apply(View.<K, OutputT>asMap()); |
| </code></pre> |
| |
| <p>Currently, the resulting map is required to fit into memory.</div> |
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| <pre>public static <K,V> <a href="../../../../../org/apache/beam/sdk/transforms/View.AsMultimap.html" title="class in org.apache.beam.sdk.transforms">View.AsMultimap</a><K,V> asMultimap()</pre> |
| <div class="block">Returns a <a href="../../../../../org/apache/beam/sdk/transforms/View.AsMultimap.html" title="class in org.apache.beam.sdk.transforms"><code>View.AsMultimap</code></a> transform that takes a <a href="../../../../../org/apache/beam/sdk/values/PCollection.html" title="class in org.apache.beam.sdk.values"><code>PCollection<KV<K, V>></code></a> as input and produces a <a href="../../../../../org/apache/beam/sdk/values/PCollectionView.html" title="interface in org.apache.beam.sdk.values"><code>PCollectionView</code></a> mapping each |
| window to its contents as a <code>Map<K, Iterable<V>></code> for use as a side |
| input. In contrast to <a href="../../../../../org/apache/beam/sdk/transforms/View.html#asMap--"><code>asMap()</code></a>, it is not required that the keys in the input |
| collection be unique. |
| |
| <pre><code> |
| PCollection<KV<K, V>> input = ... // maybe more than one occurrence of a some keys |
| PCollectionView<Map<K, Iterable<V>>> output = input.apply(View.<K, V>asMultimap()); |
| </code></pre></div> |
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