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| <div class="subTitle">org.apache.kafka.streams.kstream</div> |
| <h2 title="Interface KGroupedStream" class="title">Interface KGroupedStream<K,V></h2> |
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| <div class="contentContainer"> |
| <div class="description"> |
| <ul class="blockList"> |
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| <dl> |
| <dt><span class="paramLabel">Type Parameters:</span></dt> |
| <dd><code>K</code> - Type of keys</dd> |
| <dd><code>V</code> - Type of values</dd> |
| </dl> |
| <hr> |
| <br> |
| <pre>public interface <span class="typeNameLabel">KGroupedStream<K,V></span></pre> |
| <div class="block"><code>KGroupedStream</code> is an abstraction of a <i>grouped</i> record stream of <a href="../../../../../org/apache/kafka/streams/KeyValue.html" title="class in org.apache.kafka.streams"><code>KeyValue</code></a> pairs. |
| It is an intermediate representation of a <a href="../../../../../org/apache/kafka/streams/kstream/KStream.html" title="interface in org.apache.kafka.streams.kstream"><code>KStream</code></a> in order to apply an aggregation operation on the original |
| <a href="../../../../../org/apache/kafka/streams/kstream/KStream.html" title="interface in org.apache.kafka.streams.kstream"><code>KStream</code></a> records. |
| <p> |
| It is an intermediate representation after a grouping of a <a href="../../../../../org/apache/kafka/streams/kstream/KStream.html" title="interface in org.apache.kafka.streams.kstream"><code>KStream</code></a> before an aggregation is applied to the |
| new partitions resulting in a <a href="../../../../../org/apache/kafka/streams/kstream/KTable.html" title="interface in org.apache.kafka.streams.kstream"><code>KTable</code></a>. |
| <p> |
| A <code>KGroupedStream</code> must be obtained from a <a href="../../../../../org/apache/kafka/streams/kstream/KStream.html" title="interface in org.apache.kafka.streams.kstream"><code>KStream</code></a> via <a href="../../../../../org/apache/kafka/streams/kstream/KStream.html#groupByKey--"><code>groupByKey()</code></a> or |
| <a href="../../../../../org/apache/kafka/streams/kstream/KStream.html#groupBy-org.apache.kafka.streams.kstream.KeyValueMapper-"><code>groupBy(...)</code></a>.</div> |
| <dl> |
| <dt><span class="seeLabel">See Also:</span></dt> |
| <dd><a href="../../../../../org/apache/kafka/streams/kstream/KStream.html" title="interface in org.apache.kafka.streams.kstream"><code>KStream</code></a></dd> |
| </dl> |
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| </a> |
| <h3>Method Summary</h3> |
| <table class="memberSummary" border="0" cellpadding="3" cellspacing="0" summary="Method Summary table, listing methods, and an explanation"> |
| <caption><span id="t0" class="activeTableTab"><span>All Methods</span><span class="tabEnd"> </span></span><span id="t2" class="tableTab"><span><a href="javascript:show(2);">Instance Methods</a></span><span class="tabEnd"> </span></span><span id="t3" class="tableTab"><span><a href="javascript:show(4);">Abstract Methods</a></span><span class="tabEnd"> </span></span></caption> |
| <tr> |
| <th class="colFirst" scope="col">Modifier and Type</th> |
| <th class="colLast" scope="col">Method and Description</th> |
| </tr> |
| <tr id="i0" class="altColor"> |
| <td class="colFirst"><code><VR> <a href="../../../../../org/apache/kafka/streams/kstream/KTable.html" title="interface in org.apache.kafka.streams.kstream">KTable</a><<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">K</a>,VR></code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html#aggregate-org.apache.kafka.streams.kstream.Initializer-org.apache.kafka.streams.kstream.Aggregator-">aggregate</a></span>(<a href="../../../../../org/apache/kafka/streams/kstream/Initializer.html" title="interface in org.apache.kafka.streams.kstream">Initializer</a><VR> initializer, |
| <a href="../../../../../org/apache/kafka/streams/kstream/Aggregator.html" title="interface in org.apache.kafka.streams.kstream">Aggregator</a><? super <a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">K</a>,? super <a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">V</a>,VR> aggregator)</code> |
| <div class="block">Aggregate the values of records in this stream by the grouped key.</div> |
| </td> |
| </tr> |
| <tr id="i1" class="rowColor"> |
| <td class="colFirst"><code><VR> <a href="../../../../../org/apache/kafka/streams/kstream/KTable.html" title="interface in org.apache.kafka.streams.kstream">KTable</a><<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">K</a>,VR></code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html#aggregate-org.apache.kafka.streams.kstream.Initializer-org.apache.kafka.streams.kstream.Aggregator-org.apache.kafka.streams.kstream.Materialized-">aggregate</a></span>(<a href="../../../../../org/apache/kafka/streams/kstream/Initializer.html" title="interface in org.apache.kafka.streams.kstream">Initializer</a><VR> initializer, |
| <a href="../../../../../org/apache/kafka/streams/kstream/Aggregator.html" title="interface in org.apache.kafka.streams.kstream">Aggregator</a><? super <a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">K</a>,? super <a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">V</a>,VR> aggregator, |
| <a href="../../../../../org/apache/kafka/streams/kstream/Materialized.html" title="class in org.apache.kafka.streams.kstream">Materialized</a><<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">K</a>,VR,<a href="../../../../../org/apache/kafka/streams/state/KeyValueStore.html" title="interface in org.apache.kafka.streams.state">KeyValueStore</a><org.apache.kafka.common.utils.Bytes,byte[]>> materialized)</code> |
| <div class="block">Aggregate the values of records in this stream by the grouped key.</div> |
| </td> |
| </tr> |
| <tr id="i2" class="altColor"> |
| <td class="colFirst"><code><VR> <a href="../../../../../org/apache/kafka/streams/kstream/KTable.html" title="interface in org.apache.kafka.streams.kstream">KTable</a><<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">K</a>,VR></code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html#aggregate-org.apache.kafka.streams.kstream.Initializer-org.apache.kafka.streams.kstream.Aggregator-org.apache.kafka.streams.kstream.Named-org.apache.kafka.streams.kstream.Materialized-">aggregate</a></span>(<a href="../../../../../org/apache/kafka/streams/kstream/Initializer.html" title="interface in org.apache.kafka.streams.kstream">Initializer</a><VR> initializer, |
| <a href="../../../../../org/apache/kafka/streams/kstream/Aggregator.html" title="interface in org.apache.kafka.streams.kstream">Aggregator</a><? super <a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">K</a>,? super <a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">V</a>,VR> aggregator, |
| <a href="../../../../../org/apache/kafka/streams/kstream/Named.html" title="class in org.apache.kafka.streams.kstream">Named</a> named, |
| <a href="../../../../../org/apache/kafka/streams/kstream/Materialized.html" title="class in org.apache.kafka.streams.kstream">Materialized</a><<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">K</a>,VR,<a href="../../../../../org/apache/kafka/streams/state/KeyValueStore.html" title="interface in org.apache.kafka.streams.state">KeyValueStore</a><org.apache.kafka.common.utils.Bytes,byte[]>> materialized)</code> |
| <div class="block">Aggregate the values of records in this stream by the grouped key.</div> |
| </td> |
| </tr> |
| <tr id="i3" class="rowColor"> |
| <td class="colFirst"><code><VOut> <a href="../../../../../org/apache/kafka/streams/kstream/CogroupedKStream.html" title="interface in org.apache.kafka.streams.kstream">CogroupedKStream</a><<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">K</a>,VOut></code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html#cogroup-org.apache.kafka.streams.kstream.Aggregator-">cogroup</a></span>(<a href="../../../../../org/apache/kafka/streams/kstream/Aggregator.html" title="interface in org.apache.kafka.streams.kstream">Aggregator</a><? super <a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">K</a>,? super <a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">V</a>,VOut> aggregator)</code> |
| <div class="block">Create a new <a href="../../../../../org/apache/kafka/streams/kstream/CogroupedKStream.html" title="interface in org.apache.kafka.streams.kstream"><code>CogroupedKStream</code></a> from the this grouped KStream to allow cogrouping other |
| <code>KGroupedStream</code> to it.</div> |
| </td> |
| </tr> |
| <tr id="i4" class="altColor"> |
| <td class="colFirst"><code><a href="../../../../../org/apache/kafka/streams/kstream/KTable.html" title="interface in org.apache.kafka.streams.kstream">KTable</a><<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">K</a>,<a href="https://docs.oracle.com/javase/8/docs/api/java/lang/Long.html?is-external=true" title="class or interface in java.lang">Long</a>></code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html#count--">count</a></span>()</code> |
| <div class="block">Count the number of records in this stream by the grouped key.</div> |
| </td> |
| </tr> |
| <tr id="i5" class="rowColor"> |
| <td class="colFirst"><code><a href="../../../../../org/apache/kafka/streams/kstream/KTable.html" title="interface in org.apache.kafka.streams.kstream">KTable</a><<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">K</a>,<a href="https://docs.oracle.com/javase/8/docs/api/java/lang/Long.html?is-external=true" title="class or interface in java.lang">Long</a>></code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html#count-org.apache.kafka.streams.kstream.Materialized-">count</a></span>(<a href="../../../../../org/apache/kafka/streams/kstream/Materialized.html" title="class in org.apache.kafka.streams.kstream">Materialized</a><<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">K</a>,<a href="https://docs.oracle.com/javase/8/docs/api/java/lang/Long.html?is-external=true" title="class or interface in java.lang">Long</a>,<a href="../../../../../org/apache/kafka/streams/state/KeyValueStore.html" title="interface in org.apache.kafka.streams.state">KeyValueStore</a><org.apache.kafka.common.utils.Bytes,byte[]>> materialized)</code> |
| <div class="block">Count the number of records in this stream by the grouped key.</div> |
| </td> |
| </tr> |
| <tr id="i6" class="altColor"> |
| <td class="colFirst"><code><a href="../../../../../org/apache/kafka/streams/kstream/KTable.html" title="interface in org.apache.kafka.streams.kstream">KTable</a><<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">K</a>,<a href="https://docs.oracle.com/javase/8/docs/api/java/lang/Long.html?is-external=true" title="class or interface in java.lang">Long</a>></code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html#count-org.apache.kafka.streams.kstream.Named-">count</a></span>(<a href="../../../../../org/apache/kafka/streams/kstream/Named.html" title="class in org.apache.kafka.streams.kstream">Named</a> named)</code> |
| <div class="block">Count the number of records in this stream by the grouped key.</div> |
| </td> |
| </tr> |
| <tr id="i7" class="rowColor"> |
| <td class="colFirst"><code><a href="../../../../../org/apache/kafka/streams/kstream/KTable.html" title="interface in org.apache.kafka.streams.kstream">KTable</a><<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">K</a>,<a href="https://docs.oracle.com/javase/8/docs/api/java/lang/Long.html?is-external=true" title="class or interface in java.lang">Long</a>></code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html#count-org.apache.kafka.streams.kstream.Named-org.apache.kafka.streams.kstream.Materialized-">count</a></span>(<a href="../../../../../org/apache/kafka/streams/kstream/Named.html" title="class in org.apache.kafka.streams.kstream">Named</a> named, |
| <a href="../../../../../org/apache/kafka/streams/kstream/Materialized.html" title="class in org.apache.kafka.streams.kstream">Materialized</a><<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">K</a>,<a href="https://docs.oracle.com/javase/8/docs/api/java/lang/Long.html?is-external=true" title="class or interface in java.lang">Long</a>,<a href="../../../../../org/apache/kafka/streams/state/KeyValueStore.html" title="interface in org.apache.kafka.streams.state">KeyValueStore</a><org.apache.kafka.common.utils.Bytes,byte[]>> materialized)</code> |
| <div class="block">Count the number of records in this stream by the grouped key.</div> |
| </td> |
| </tr> |
| <tr id="i8" class="altColor"> |
| <td class="colFirst"><code><a href="../../../../../org/apache/kafka/streams/kstream/KTable.html" title="interface in org.apache.kafka.streams.kstream">KTable</a><<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">K</a>,<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">V</a>></code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html#reduce-org.apache.kafka.streams.kstream.Reducer-">reduce</a></span>(<a href="../../../../../org/apache/kafka/streams/kstream/Reducer.html" title="interface in org.apache.kafka.streams.kstream">Reducer</a><<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">V</a>> reducer)</code> |
| <div class="block">Combine the values of records in this stream by the grouped key.</div> |
| </td> |
| </tr> |
| <tr id="i9" class="rowColor"> |
| <td class="colFirst"><code><a href="../../../../../org/apache/kafka/streams/kstream/KTable.html" title="interface in org.apache.kafka.streams.kstream">KTable</a><<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">K</a>,<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">V</a>></code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html#reduce-org.apache.kafka.streams.kstream.Reducer-org.apache.kafka.streams.kstream.Materialized-">reduce</a></span>(<a href="../../../../../org/apache/kafka/streams/kstream/Reducer.html" title="interface in org.apache.kafka.streams.kstream">Reducer</a><<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">V</a>> reducer, |
| <a href="../../../../../org/apache/kafka/streams/kstream/Materialized.html" title="class in org.apache.kafka.streams.kstream">Materialized</a><<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">K</a>,<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">V</a>,<a href="../../../../../org/apache/kafka/streams/state/KeyValueStore.html" title="interface in org.apache.kafka.streams.state">KeyValueStore</a><org.apache.kafka.common.utils.Bytes,byte[]>> materialized)</code> |
| <div class="block">Combine the value of records in this stream by the grouped key.</div> |
| </td> |
| </tr> |
| <tr id="i10" class="altColor"> |
| <td class="colFirst"><code><a href="../../../../../org/apache/kafka/streams/kstream/KTable.html" title="interface in org.apache.kafka.streams.kstream">KTable</a><<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">K</a>,<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">V</a>></code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html#reduce-org.apache.kafka.streams.kstream.Reducer-org.apache.kafka.streams.kstream.Named-org.apache.kafka.streams.kstream.Materialized-">reduce</a></span>(<a href="../../../../../org/apache/kafka/streams/kstream/Reducer.html" title="interface in org.apache.kafka.streams.kstream">Reducer</a><<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">V</a>> reducer, |
| <a href="../../../../../org/apache/kafka/streams/kstream/Named.html" title="class in org.apache.kafka.streams.kstream">Named</a> named, |
| <a href="../../../../../org/apache/kafka/streams/kstream/Materialized.html" title="class in org.apache.kafka.streams.kstream">Materialized</a><<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">K</a>,<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">V</a>,<a href="../../../../../org/apache/kafka/streams/state/KeyValueStore.html" title="interface in org.apache.kafka.streams.state">KeyValueStore</a><org.apache.kafka.common.utils.Bytes,byte[]>> materialized)</code> |
| <div class="block">Combine the value of records in this stream by the grouped key.</div> |
| </td> |
| </tr> |
| <tr id="i11" class="rowColor"> |
| <td class="colFirst"><code><a href="../../../../../org/apache/kafka/streams/kstream/SessionWindowedKStream.html" title="interface in org.apache.kafka.streams.kstream">SessionWindowedKStream</a><<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">K</a>,<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">V</a>></code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html#windowedBy-org.apache.kafka.streams.kstream.SessionWindows-">windowedBy</a></span>(<a href="../../../../../org/apache/kafka/streams/kstream/SessionWindows.html" title="class in org.apache.kafka.streams.kstream">SessionWindows</a> windows)</code> |
| <div class="block">Create a new <a href="../../../../../org/apache/kafka/streams/kstream/SessionWindowedKStream.html" title="interface in org.apache.kafka.streams.kstream"><code>SessionWindowedKStream</code></a> instance that can be used to perform session windowed aggregations.</div> |
| </td> |
| </tr> |
| <tr id="i12" class="altColor"> |
| <td class="colFirst"><code><a href="../../../../../org/apache/kafka/streams/kstream/TimeWindowedKStream.html" title="interface in org.apache.kafka.streams.kstream">TimeWindowedKStream</a><<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">K</a>,<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">V</a>></code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html#windowedBy-org.apache.kafka.streams.kstream.SlidingWindows-">windowedBy</a></span>(<a href="../../../../../org/apache/kafka/streams/kstream/SlidingWindows.html" title="class in org.apache.kafka.streams.kstream">SlidingWindows</a> windows)</code> |
| <div class="block">Create a new <a href="../../../../../org/apache/kafka/streams/kstream/TimeWindowedKStream.html" title="interface in org.apache.kafka.streams.kstream"><code>TimeWindowedKStream</code></a> instance that can be used to perform sliding windowed aggregations.</div> |
| </td> |
| </tr> |
| <tr id="i13" class="rowColor"> |
| <td class="colFirst"><code><W extends <a href="../../../../../org/apache/kafka/streams/kstream/Window.html" title="class in org.apache.kafka.streams.kstream">Window</a>><br><a href="../../../../../org/apache/kafka/streams/kstream/TimeWindowedKStream.html" title="interface in org.apache.kafka.streams.kstream">TimeWindowedKStream</a><<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">K</a>,<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">V</a>></code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html#windowedBy-org.apache.kafka.streams.kstream.Windows-">windowedBy</a></span>(<a href="../../../../../org/apache/kafka/streams/kstream/Windows.html" title="class in org.apache.kafka.streams.kstream">Windows</a><W> windows)</code> |
| <div class="block">Create a new <a href="../../../../../org/apache/kafka/streams/kstream/TimeWindowedKStream.html" title="interface in org.apache.kafka.streams.kstream"><code>TimeWindowedKStream</code></a> instance that can be used to perform windowed aggregations.</div> |
| </td> |
| </tr> |
| </table> |
| </li> |
| </ul> |
| </li> |
| </ul> |
| </div> |
| <div class="details"> |
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| <!-- ============ METHOD DETAIL ========== --> |
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| <li class="blockList"><a name="method.detail"> |
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| <h3>Method Detail</h3> |
| <a name="count--"> |
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| <h4>count</h4> |
| <pre><a href="../../../../../org/apache/kafka/streams/kstream/KTable.html" title="interface in org.apache.kafka.streams.kstream">KTable</a><<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">K</a>,<a href="https://docs.oracle.com/javase/8/docs/api/java/lang/Long.html?is-external=true" title="class or interface in java.lang">Long</a>> count()</pre> |
| <div class="block">Count the number of records in this stream by the grouped key. |
| Records with <code>null</code> key or value are ignored. |
| The result is written into a local <a href="../../../../../org/apache/kafka/streams/state/KeyValueStore.html" title="interface in org.apache.kafka.streams.state"><code>KeyValueStore</code></a> (which is basically an ever-updating materialized view). |
| Furthermore, updates to the store are sent downstream into a <a href="../../../../../org/apache/kafka/streams/kstream/KTable.html" title="interface in org.apache.kafka.streams.kstream"><code>KTable</code></a> changelog stream. |
| <p> |
| Not all updates might get sent downstream, as an internal cache is used to deduplicate consecutive updates to |
| the same key. |
| The rate of propagated updates depends on your input data rate, the number of distinct keys, the number of |
| parallel running Kafka Streams instances, and the <a href="../../../../../org/apache/kafka/streams/StreamsConfig.html" title="class in org.apache.kafka.streams"><code>configuration</code></a> parameters for |
| <a href="../../../../../org/apache/kafka/streams/StreamsConfig.html#CACHE_MAX_BYTES_BUFFERING_CONFIG"><code>cache size</code></a>, and |
| <a href="../../../../../org/apache/kafka/streams/StreamsConfig.html#COMMIT_INTERVAL_MS_CONFIG"><code>commit intervall</code></a>. |
| <p> |
| For failure and recovery the store will be backed by an internal changelog topic that will be created in Kafka. |
| The changelog topic will be named "${applicationId}-${internalStoreName}-changelog", where "applicationId" is |
| user-specified in <a href="../../../../../org/apache/kafka/streams/StreamsConfig.html" title="class in org.apache.kafka.streams"><code>StreamsConfig</code></a> via parameter |
| <a href="../../../../../org/apache/kafka/streams/StreamsConfig.html#APPLICATION_ID_CONFIG"><code>APPLICATION_ID_CONFIG</code></a>, "internalStoreName" is an internal name |
| and "-changelog" is a fixed suffix. |
| Note that the internal store name may not be queryable through Interactive Queries. |
| |
| You can retrieve all generated internal topic names via <a href="../../../../../org/apache/kafka/streams/Topology.html#describe--"><code>Topology.describe()</code></a>.</div> |
| <dl> |
| <dt><span class="returnLabel">Returns:</span></dt> |
| <dd>a <a href="../../../../../org/apache/kafka/streams/kstream/KTable.html" title="interface in org.apache.kafka.streams.kstream"><code>KTable</code></a> that contains "update" records with unmodified keys and <a href="https://docs.oracle.com/javase/8/docs/api/java/lang/Long.html?is-external=true" title="class or interface in java.lang"><code>Long</code></a> values that |
| represent the latest (rolling) count (i.e., number of records) for each key</dd> |
| </dl> |
| </li> |
| </ul> |
| <a name="count-org.apache.kafka.streams.kstream.Named-"> |
| <!-- --> |
| </a> |
| <ul class="blockList"> |
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| <h4>count</h4> |
| <pre><a href="../../../../../org/apache/kafka/streams/kstream/KTable.html" title="interface in org.apache.kafka.streams.kstream">KTable</a><<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">K</a>,<a href="https://docs.oracle.com/javase/8/docs/api/java/lang/Long.html?is-external=true" title="class or interface in java.lang">Long</a>> count(<a href="../../../../../org/apache/kafka/streams/kstream/Named.html" title="class in org.apache.kafka.streams.kstream">Named</a> named)</pre> |
| <div class="block">Count the number of records in this stream by the grouped key. |
| Records with <code>null</code> key or value are ignored. |
| The result is written into a local <a href="../../../../../org/apache/kafka/streams/state/KeyValueStore.html" title="interface in org.apache.kafka.streams.state"><code>KeyValueStore</code></a> (which is basically an ever-updating materialized view). |
| Furthermore, updates to the store are sent downstream into a <a href="../../../../../org/apache/kafka/streams/kstream/KTable.html" title="interface in org.apache.kafka.streams.kstream"><code>KTable</code></a> changelog stream. |
| <p> |
| Not all updates might get sent downstream, as an internal cache is used to deduplicate consecutive updates to |
| the same key. |
| The rate of propagated updates depends on your input data rate, the number of distinct keys, the number of |
| parallel running Kafka Streams instances, and the <a href="../../../../../org/apache/kafka/streams/StreamsConfig.html" title="class in org.apache.kafka.streams"><code>configuration</code></a> parameters for |
| <a href="../../../../../org/apache/kafka/streams/StreamsConfig.html#CACHE_MAX_BYTES_BUFFERING_CONFIG"><code>cache size</code></a>, and |
| <a href="../../../../../org/apache/kafka/streams/StreamsConfig.html#COMMIT_INTERVAL_MS_CONFIG"><code>commit intervall</code></a>. |
| <p> |
| For failure and recovery the store will be backed by an internal changelog topic that will be created in Kafka. |
| The changelog topic will be named "${applicationId}-${internalStoreName}-changelog", where "applicationId" is |
| user-specified in <a href="../../../../../org/apache/kafka/streams/StreamsConfig.html" title="class in org.apache.kafka.streams"><code>StreamsConfig</code></a> via parameter |
| <a href="../../../../../org/apache/kafka/streams/StreamsConfig.html#APPLICATION_ID_CONFIG"><code>APPLICATION_ID_CONFIG</code></a>, "internalStoreName" is an internal name |
| and "-changelog" is a fixed suffix. |
| Note that the internal store name may not be queryable through Interactive Queries. |
| |
| You can retrieve all generated internal topic names via <a href="../../../../../org/apache/kafka/streams/Topology.html#describe--"><code>Topology.describe()</code></a>.</div> |
| <dl> |
| <dt><span class="paramLabel">Parameters:</span></dt> |
| <dd><code>named</code> - a <a href="../../../../../org/apache/kafka/streams/kstream/Named.html" title="class in org.apache.kafka.streams.kstream"><code>Named</code></a> config used to name the processor in the topology</dd> |
| <dt><span class="returnLabel">Returns:</span></dt> |
| <dd>a <a href="../../../../../org/apache/kafka/streams/kstream/KTable.html" title="interface in org.apache.kafka.streams.kstream"><code>KTable</code></a> that contains "update" records with unmodified keys and <a href="https://docs.oracle.com/javase/8/docs/api/java/lang/Long.html?is-external=true" title="class or interface in java.lang"><code>Long</code></a> values that |
| represent the latest (rolling) count (i.e., number of records) for each key</dd> |
| </dl> |
| </li> |
| </ul> |
| <a name="count-org.apache.kafka.streams.kstream.Materialized-"> |
| <!-- --> |
| </a> |
| <ul class="blockList"> |
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| <h4>count</h4> |
| <pre><a href="../../../../../org/apache/kafka/streams/kstream/KTable.html" title="interface in org.apache.kafka.streams.kstream">KTable</a><<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">K</a>,<a href="https://docs.oracle.com/javase/8/docs/api/java/lang/Long.html?is-external=true" title="class or interface in java.lang">Long</a>> count(<a href="../../../../../org/apache/kafka/streams/kstream/Materialized.html" title="class in org.apache.kafka.streams.kstream">Materialized</a><<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">K</a>,<a href="https://docs.oracle.com/javase/8/docs/api/java/lang/Long.html?is-external=true" title="class or interface in java.lang">Long</a>,<a href="../../../../../org/apache/kafka/streams/state/KeyValueStore.html" title="interface in org.apache.kafka.streams.state">KeyValueStore</a><org.apache.kafka.common.utils.Bytes,byte[]>> materialized)</pre> |
| <div class="block">Count the number of records in this stream by the grouped key. |
| Records with <code>null</code> key or value are ignored. |
| The result is written into a local <a href="../../../../../org/apache/kafka/streams/state/KeyValueStore.html" title="interface in org.apache.kafka.streams.state"><code>KeyValueStore</code></a> (which is basically an ever-updating materialized view) |
| provided by the given store name in <code>materialized</code>. |
| Furthermore, updates to the store are sent downstream into a <a href="../../../../../org/apache/kafka/streams/kstream/KTable.html" title="interface in org.apache.kafka.streams.kstream"><code>KTable</code></a> changelog stream. |
| <p> |
| Not all updates might get sent downstream, as an internal cache is used to deduplicate consecutive updates to |
| the same key. |
| The rate of propagated updates depends on your input data rate, the number of distinct keys, the number of |
| parallel running Kafka Streams instances, and the <a href="../../../../../org/apache/kafka/streams/StreamsConfig.html" title="class in org.apache.kafka.streams"><code>configuration</code></a> parameters for |
| <a href="../../../../../org/apache/kafka/streams/StreamsConfig.html#CACHE_MAX_BYTES_BUFFERING_CONFIG"><code>cache size</code></a>, and |
| <a href="../../../../../org/apache/kafka/streams/StreamsConfig.html#COMMIT_INTERVAL_MS_CONFIG"><code>commit intervall</code></a>. |
| <p> |
| To query the local <a href="../../../../../org/apache/kafka/streams/state/ReadOnlyKeyValueStore.html" title="interface in org.apache.kafka.streams.state"><code>ReadOnlyKeyValueStore</code></a> it must be obtained via |
| <a href="../../../../../org/apache/kafka/streams/KafkaStreams.html#store-org.apache.kafka.streams.StoreQueryParameters-"><code>KafkaStreams#store(...)</code></a>. |
| <pre><code> |
| KafkaStreams streams = ... // counting words |
| String queryableStoreName = "storeName"; // the store name should be the name of the store as defined by the Materialized instance |
| ReadOnlyKeyValueStore<K, ValueAndTimestamp<Long>> localStore = streams.store(queryableStoreName, QueryableStoreTypes.<K, ValueAndTimestamp<Long>>timestampedKeyValueStore()); |
| K key = "some-word"; |
| ValueAndTimestamp<Long> countForWord = localStore.get(key); // key must be local (application state is shared over all running Kafka Streams instances) |
| </code></pre> |
| For non-local keys, a custom RPC mechanism must be implemented using <a href="../../../../../org/apache/kafka/streams/KafkaStreams.html#allMetadata--"><code>KafkaStreams.allMetadata()</code></a> to |
| query the value of the key on a parallel running instance of your Kafka Streams application. |
| |
| <p> |
| For failure and recovery the store will be backed by an internal changelog topic that will be created in Kafka. |
| Therefore, the store name defined by the Materialized instance must be a valid Kafka topic name and cannot contain characters other than ASCII |
| alphanumerics, '.', '_' and '-'. |
| The changelog topic will be named "${applicationId}-${storeName}-changelog", where "applicationId" is |
| user-specified in <a href="../../../../../org/apache/kafka/streams/StreamsConfig.html" title="class in org.apache.kafka.streams"><code>StreamsConfig</code></a> via parameter |
| <a href="../../../../../org/apache/kafka/streams/StreamsConfig.html#APPLICATION_ID_CONFIG"><code>APPLICATION_ID_CONFIG</code></a>, "storeName" is the |
| provide store name defined in <code>Materialized</code>, and "-changelog" is a fixed suffix. |
| |
| You can retrieve all generated internal topic names via <a href="../../../../../org/apache/kafka/streams/Topology.html#describe--"><code>Topology.describe()</code></a>.</div> |
| <dl> |
| <dt><span class="paramLabel">Parameters:</span></dt> |
| <dd><code>materialized</code> - an instance of <a href="../../../../../org/apache/kafka/streams/kstream/Materialized.html" title="class in org.apache.kafka.streams.kstream"><code>Materialized</code></a> used to materialize a state store. Cannot be <code>null</code>. |
| Note: the valueSerde will be automatically set to <a href="../../../../../org/apache/kafka/common/serialization/Serdes.html#Long--"><code>Serdes#Long()</code></a> |
| if there is no valueSerde provided</dd> |
| <dt><span class="returnLabel">Returns:</span></dt> |
| <dd>a <a href="../../../../../org/apache/kafka/streams/kstream/KTable.html" title="interface in org.apache.kafka.streams.kstream"><code>KTable</code></a> that contains "update" records with unmodified keys and <a href="https://docs.oracle.com/javase/8/docs/api/java/lang/Long.html?is-external=true" title="class or interface in java.lang"><code>Long</code></a> values that |
| represent the latest (rolling) count (i.e., number of records) for each key</dd> |
| </dl> |
| </li> |
| </ul> |
| <a name="count-org.apache.kafka.streams.kstream.Named-org.apache.kafka.streams.kstream.Materialized-"> |
| <!-- --> |
| </a> |
| <ul class="blockList"> |
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| <h4>count</h4> |
| <pre><a href="../../../../../org/apache/kafka/streams/kstream/KTable.html" title="interface in org.apache.kafka.streams.kstream">KTable</a><<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">K</a>,<a href="https://docs.oracle.com/javase/8/docs/api/java/lang/Long.html?is-external=true" title="class or interface in java.lang">Long</a>> count(<a href="../../../../../org/apache/kafka/streams/kstream/Named.html" title="class in org.apache.kafka.streams.kstream">Named</a> named, |
| <a href="../../../../../org/apache/kafka/streams/kstream/Materialized.html" title="class in org.apache.kafka.streams.kstream">Materialized</a><<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">K</a>,<a href="https://docs.oracle.com/javase/8/docs/api/java/lang/Long.html?is-external=true" title="class or interface in java.lang">Long</a>,<a href="../../../../../org/apache/kafka/streams/state/KeyValueStore.html" title="interface in org.apache.kafka.streams.state">KeyValueStore</a><org.apache.kafka.common.utils.Bytes,byte[]>> materialized)</pre> |
| <div class="block">Count the number of records in this stream by the grouped key. |
| Records with <code>null</code> key or value are ignored. |
| The result is written into a local <a href="../../../../../org/apache/kafka/streams/state/KeyValueStore.html" title="interface in org.apache.kafka.streams.state"><code>KeyValueStore</code></a> (which is basically an ever-updating materialized view) |
| provided by the given store name in <code>materialized</code>. |
| Furthermore, updates to the store are sent downstream into a <a href="../../../../../org/apache/kafka/streams/kstream/KTable.html" title="interface in org.apache.kafka.streams.kstream"><code>KTable</code></a> changelog stream. |
| <p> |
| Not all updates might get sent downstream, as an internal cache is used to deduplicate consecutive updates to |
| the same key. |
| The rate of propagated updates depends on your input data rate, the number of distinct keys, the number of |
| parallel running Kafka Streams instances, and the <a href="../../../../../org/apache/kafka/streams/StreamsConfig.html" title="class in org.apache.kafka.streams"><code>configuration</code></a> parameters for |
| <a href="../../../../../org/apache/kafka/streams/StreamsConfig.html#CACHE_MAX_BYTES_BUFFERING_CONFIG"><code>cache size</code></a>, and |
| <a href="../../../../../org/apache/kafka/streams/StreamsConfig.html#COMMIT_INTERVAL_MS_CONFIG"><code>commit intervall</code></a>. |
| <p> |
| To query the local <a href="../../../../../org/apache/kafka/streams/state/ReadOnlyKeyValueStore.html" title="interface in org.apache.kafka.streams.state"><code>ReadOnlyKeyValueStore</code></a> it must be obtained via |
| <a href="../../../../../org/apache/kafka/streams/KafkaStreams.html#store-org.apache.kafka.streams.StoreQueryParameters-"><code>KafkaStreams#store(...)</code></a>. |
| <pre><code> |
| KafkaStreams streams = ... // counting words |
| String queryableStoreName = "storeName"; // the store name should be the name of the store as defined by the Materialized instance |
| ReadOnlyKeyValueStore<K, ValueAndTimestamp<Long>> localStore = streams.store(queryableStoreName, QueryableStoreTypes.<K, ValueAndTimestamp<Long>>timestampedKeyValueStore()); |
| K key = "some-word"; |
| ValueAndTimestamp<Long> countForWord = localStore.get(key); // key must be local (application state is shared over all running Kafka Streams instances) |
| </code></pre> |
| For non-local keys, a custom RPC mechanism must be implemented using <a href="../../../../../org/apache/kafka/streams/KafkaStreams.html#allMetadata--"><code>KafkaStreams.allMetadata()</code></a> to |
| query the value of the key on a parallel running instance of your Kafka Streams application. |
| |
| <p> |
| For failure and recovery the store will be backed by an internal changelog topic that will be created in Kafka. |
| Therefore, the store name defined by the Materialized instance must be a valid Kafka topic name and cannot contain characters other than ASCII |
| alphanumerics, '.', '_' and '-'. |
| The changelog topic will be named "${applicationId}-${storeName}-changelog", where "applicationId" is |
| user-specified in <a href="../../../../../org/apache/kafka/streams/StreamsConfig.html" title="class in org.apache.kafka.streams"><code>StreamsConfig</code></a> via parameter |
| <a href="../../../../../org/apache/kafka/streams/StreamsConfig.html#APPLICATION_ID_CONFIG"><code>APPLICATION_ID_CONFIG</code></a>, "storeName" is the |
| provide store name defined in <code>Materialized</code>, and "-changelog" is a fixed suffix. |
| |
| You can retrieve all generated internal topic names via <a href="../../../../../org/apache/kafka/streams/Topology.html#describe--"><code>Topology.describe()</code></a>.</div> |
| <dl> |
| <dt><span class="paramLabel">Parameters:</span></dt> |
| <dd><code>named</code> - a <a href="../../../../../org/apache/kafka/streams/kstream/Named.html" title="class in org.apache.kafka.streams.kstream"><code>Named</code></a> config used to name the processor in the topology</dd> |
| <dd><code>materialized</code> - an instance of <a href="../../../../../org/apache/kafka/streams/kstream/Materialized.html" title="class in org.apache.kafka.streams.kstream"><code>Materialized</code></a> used to materialize a state store. Cannot be <code>null</code>. |
| Note: the valueSerde will be automatically set to <a href="../../../../../org/apache/kafka/common/serialization/Serdes.html#Long--"><code>Serdes#Long()</code></a> |
| if there is no valueSerde provided</dd> |
| <dt><span class="returnLabel">Returns:</span></dt> |
| <dd>a <a href="../../../../../org/apache/kafka/streams/kstream/KTable.html" title="interface in org.apache.kafka.streams.kstream"><code>KTable</code></a> that contains "update" records with unmodified keys and <a href="https://docs.oracle.com/javase/8/docs/api/java/lang/Long.html?is-external=true" title="class or interface in java.lang"><code>Long</code></a> values that |
| represent the latest (rolling) count (i.e., number of records) for each key</dd> |
| </dl> |
| </li> |
| </ul> |
| <a name="reduce-org.apache.kafka.streams.kstream.Reducer-"> |
| <!-- --> |
| </a> |
| <ul class="blockList"> |
| <li class="blockList"> |
| <h4>reduce</h4> |
| <pre><a href="../../../../../org/apache/kafka/streams/kstream/KTable.html" title="interface in org.apache.kafka.streams.kstream">KTable</a><<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">K</a>,<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">V</a>> reduce(<a href="../../../../../org/apache/kafka/streams/kstream/Reducer.html" title="interface in org.apache.kafka.streams.kstream">Reducer</a><<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">V</a>> reducer)</pre> |
| <div class="block">Combine the values of records in this stream by the grouped key. |
| Records with <code>null</code> key or value are ignored. |
| Combining implies that the type of the aggregate result is the same as the type of the input value |
| (c.f. <a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html#aggregate-org.apache.kafka.streams.kstream.Initializer-org.apache.kafka.streams.kstream.Aggregator-"><code>aggregate(Initializer, Aggregator)</code></a>). |
| <p> |
| The specified <a href="../../../../../org/apache/kafka/streams/kstream/Reducer.html" title="interface in org.apache.kafka.streams.kstream"><code>Reducer</code></a> is applied for each input record and computes a new aggregate using the current |
| aggregate and the record's value. |
| If there is no current aggregate the <a href="../../../../../org/apache/kafka/streams/kstream/Reducer.html" title="interface in org.apache.kafka.streams.kstream"><code>Reducer</code></a> is not applied and the new aggregate will be the record's |
| value as-is. |
| Thus, <code>reduce(Reducer)</code> can be used to compute aggregate functions like sum, min, or max. |
| <p> |
| Not all updates might get sent downstream, as an internal cache is used to deduplicate consecutive updates to |
| the same key. |
| The rate of propagated updates depends on your input data rate, the number of distinct keys, the number of |
| parallel running Kafka Streams instances, and the <a href="../../../../../org/apache/kafka/streams/StreamsConfig.html" title="class in org.apache.kafka.streams"><code>configuration</code></a> parameters for |
| <a href="../../../../../org/apache/kafka/streams/StreamsConfig.html#CACHE_MAX_BYTES_BUFFERING_CONFIG"><code>cache size</code></a>, and |
| <a href="../../../../../org/apache/kafka/streams/StreamsConfig.html#COMMIT_INTERVAL_MS_CONFIG"><code>commit intervall</code></a>. |
| |
| <p> |
| For failure and recovery the store will be backed by an internal changelog topic that will be created in Kafka. |
| The changelog topic will be named "${applicationId}-${internalStoreName}-changelog", where "applicationId" is |
| user-specified in <a href="../../../../../org/apache/kafka/streams/StreamsConfig.html" title="class in org.apache.kafka.streams"><code>StreamsConfig</code></a> via parameter |
| <a href="../../../../../org/apache/kafka/streams/StreamsConfig.html#APPLICATION_ID_CONFIG"><code>APPLICATION_ID_CONFIG</code></a>, "internalStoreName" is an internal name |
| and "-changelog" is a fixed suffix. |
| Note that the internal store name may not be queryable through Interactive Queries. |
| |
| You can retrieve all generated internal topic names via <a href="../../../../../org/apache/kafka/streams/Topology.html#describe--"><code>Topology.describe()</code></a>.</div> |
| <dl> |
| <dt><span class="paramLabel">Parameters:</span></dt> |
| <dd><code>reducer</code> - a <a href="../../../../../org/apache/kafka/streams/kstream/Reducer.html" title="interface in org.apache.kafka.streams.kstream"><code>Reducer</code></a> that computes a new aggregate result. Cannot be <code>null</code>.</dd> |
| <dt><span class="returnLabel">Returns:</span></dt> |
| <dd>a <a href="../../../../../org/apache/kafka/streams/kstream/KTable.html" title="interface in org.apache.kafka.streams.kstream"><code>KTable</code></a> that contains "update" records with unmodified keys, and values that represent the |
| latest (rolling) aggregate for each key. If the reduce function returns <code>null</code>, it is then interpreted as |
| deletion for the key, and future messages of the same key coming from upstream operators |
| will be handled as newly initialized value.</dd> |
| </dl> |
| </li> |
| </ul> |
| <a name="reduce-org.apache.kafka.streams.kstream.Reducer-org.apache.kafka.streams.kstream.Materialized-"> |
| <!-- --> |
| </a> |
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| <h4>reduce</h4> |
| <pre><a href="../../../../../org/apache/kafka/streams/kstream/KTable.html" title="interface in org.apache.kafka.streams.kstream">KTable</a><<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">K</a>,<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">V</a>> reduce(<a href="../../../../../org/apache/kafka/streams/kstream/Reducer.html" title="interface in org.apache.kafka.streams.kstream">Reducer</a><<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">V</a>> reducer, |
| <a href="../../../../../org/apache/kafka/streams/kstream/Materialized.html" title="class in org.apache.kafka.streams.kstream">Materialized</a><<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">K</a>,<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">V</a>,<a href="../../../../../org/apache/kafka/streams/state/KeyValueStore.html" title="interface in org.apache.kafka.streams.state">KeyValueStore</a><org.apache.kafka.common.utils.Bytes,byte[]>> materialized)</pre> |
| <div class="block">Combine the value of records in this stream by the grouped key. |
| Records with <code>null</code> key or value are ignored. |
| Combining implies that the type of the aggregate result is the same as the type of the input value |
| (c.f. <a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html#aggregate-org.apache.kafka.streams.kstream.Initializer-org.apache.kafka.streams.kstream.Aggregator-org.apache.kafka.streams.kstream.Materialized-"><code>aggregate(Initializer, Aggregator, Materialized)</code></a>). |
| The result is written into a local <a href="../../../../../org/apache/kafka/streams/state/KeyValueStore.html" title="interface in org.apache.kafka.streams.state"><code>KeyValueStore</code></a> (which is basically an ever-updating materialized view) |
| provided by the given store name in <code>materialized</code>. |
| Furthermore, updates to the store are sent downstream into a <a href="../../../../../org/apache/kafka/streams/kstream/KTable.html" title="interface in org.apache.kafka.streams.kstream"><code>KTable</code></a> changelog stream. |
| <p> |
| The specified <a href="../../../../../org/apache/kafka/streams/kstream/Reducer.html" title="interface in org.apache.kafka.streams.kstream"><code>Reducer</code></a> is applied for each input record and computes a new aggregate using the current |
| aggregate (first argument) and the record's value (second argument): |
| <pre><code> |
| // At the example of a Reducer<Long> |
| new Reducer<Long>() { |
| public Long apply(Long aggValue, Long currValue) { |
| return aggValue + currValue; |
| } |
| } |
| </code></pre> |
| <p> |
| If there is no current aggregate the <a href="../../../../../org/apache/kafka/streams/kstream/Reducer.html" title="interface in org.apache.kafka.streams.kstream"><code>Reducer</code></a> is not applied and the new aggregate will be the record's |
| value as-is. |
| Thus, <code>reduce(Reducer, Materialized)</code> can be used to compute aggregate functions like sum, min, or |
| max. |
| <p> |
| Not all updates might get sent downstream, as an internal cache is used to deduplicate consecutive updates to |
| the same key. |
| The rate of propagated updates depends on your input data rate, the number of distinct keys, the number of |
| parallel running Kafka Streams instances, and the <a href="../../../../../org/apache/kafka/streams/StreamsConfig.html" title="class in org.apache.kafka.streams"><code>configuration</code></a> parameters for |
| <a href="../../../../../org/apache/kafka/streams/StreamsConfig.html#CACHE_MAX_BYTES_BUFFERING_CONFIG"><code>cache size</code></a>, and |
| <a href="../../../../../org/apache/kafka/streams/StreamsConfig.html#COMMIT_INTERVAL_MS_CONFIG"><code>commit intervall</code></a>. |
| <p> |
| To query the local <a href="../../../../../org/apache/kafka/streams/state/ReadOnlyKeyValueStore.html" title="interface in org.apache.kafka.streams.state"><code>ReadOnlyKeyValueStore</code></a> it must be obtained via |
| <a href="../../../../../org/apache/kafka/streams/KafkaStreams.html#store-org.apache.kafka.streams.StoreQueryParameters-"><code>KafkaStreams#store(...)</code></a>. |
| <pre><code> |
| KafkaStreams streams = ... // compute sum |
| String queryableStoreName = "storeName" // the store name should be the name of the store as defined by the Materialized instance |
| ReadOnlyKeyValueStore<K, ValueAndTimestamp<V>> localStore = streams.store(queryableStoreName, QueryableStoreTypes.<K, ValueAndTimestamp<V>>timestampedKeyValueStore()); |
| K key = "some-key"; |
| ValueAndTimestamp<V> reduceForKey = localStore.get(key); // key must be local (application state is shared over all running Kafka Streams instances) |
| </code></pre> |
| For non-local keys, a custom RPC mechanism must be implemented using <a href="../../../../../org/apache/kafka/streams/KafkaStreams.html#allMetadata--"><code>KafkaStreams.allMetadata()</code></a> to |
| query the value of the key on a parallel running instance of your Kafka Streams application. |
| |
| <p> |
| For failure and recovery the store will be backed by an internal changelog topic that will be created in Kafka. |
| The changelog topic will be named "${applicationId}-${internalStoreName}-changelog", where "applicationId" is |
| user-specified in <a href="../../../../../org/apache/kafka/streams/StreamsConfig.html" title="class in org.apache.kafka.streams"><code>StreamsConfig</code></a> via parameter |
| <a href="../../../../../org/apache/kafka/streams/StreamsConfig.html#APPLICATION_ID_CONFIG"><code>APPLICATION_ID_CONFIG</code></a>, "internalStoreName" is an internal name |
| and "-changelog" is a fixed suffix. |
| Note that the internal store name may not be queryable through Interactive Queries. |
| |
| You can retrieve all generated internal topic names via <a href="../../../../../org/apache/kafka/streams/Topology.html#describe--"><code>Topology.describe()</code></a>.</div> |
| <dl> |
| <dt><span class="paramLabel">Parameters:</span></dt> |
| <dd><code>reducer</code> - a <a href="../../../../../org/apache/kafka/streams/kstream/Reducer.html" title="interface in org.apache.kafka.streams.kstream"><code>Reducer</code></a> that computes a new aggregate result. Cannot be <code>null</code>.</dd> |
| <dd><code>materialized</code> - an instance of <a href="../../../../../org/apache/kafka/streams/kstream/Materialized.html" title="class in org.apache.kafka.streams.kstream"><code>Materialized</code></a> used to materialize a state store. Cannot be <code>null</code>.</dd> |
| <dt><span class="returnLabel">Returns:</span></dt> |
| <dd>a <a href="../../../../../org/apache/kafka/streams/kstream/KTable.html" title="interface in org.apache.kafka.streams.kstream"><code>KTable</code></a> that contains "update" records with unmodified keys, and values that represent the |
| latest (rolling) aggregate for each key</dd> |
| </dl> |
| </li> |
| </ul> |
| <a name="reduce-org.apache.kafka.streams.kstream.Reducer-org.apache.kafka.streams.kstream.Named-org.apache.kafka.streams.kstream.Materialized-"> |
| <!-- --> |
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| <ul class="blockList"> |
| <li class="blockList"> |
| <h4>reduce</h4> |
| <pre><a href="../../../../../org/apache/kafka/streams/kstream/KTable.html" title="interface in org.apache.kafka.streams.kstream">KTable</a><<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">K</a>,<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">V</a>> reduce(<a href="../../../../../org/apache/kafka/streams/kstream/Reducer.html" title="interface in org.apache.kafka.streams.kstream">Reducer</a><<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">V</a>> reducer, |
| <a href="../../../../../org/apache/kafka/streams/kstream/Named.html" title="class in org.apache.kafka.streams.kstream">Named</a> named, |
| <a href="../../../../../org/apache/kafka/streams/kstream/Materialized.html" title="class in org.apache.kafka.streams.kstream">Materialized</a><<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">K</a>,<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">V</a>,<a href="../../../../../org/apache/kafka/streams/state/KeyValueStore.html" title="interface in org.apache.kafka.streams.state">KeyValueStore</a><org.apache.kafka.common.utils.Bytes,byte[]>> materialized)</pre> |
| <div class="block">Combine the value of records in this stream by the grouped key. |
| Records with <code>null</code> key or value are ignored. |
| Combining implies that the type of the aggregate result is the same as the type of the input value |
| (c.f. <a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html#aggregate-org.apache.kafka.streams.kstream.Initializer-org.apache.kafka.streams.kstream.Aggregator-org.apache.kafka.streams.kstream.Materialized-"><code>aggregate(Initializer, Aggregator, Materialized)</code></a>). |
| The result is written into a local <a href="../../../../../org/apache/kafka/streams/state/KeyValueStore.html" title="interface in org.apache.kafka.streams.state"><code>KeyValueStore</code></a> (which is basically an ever-updating materialized view) |
| provided by the given store name in <code>materialized</code>. |
| Furthermore, updates to the store are sent downstream into a <a href="../../../../../org/apache/kafka/streams/kstream/KTable.html" title="interface in org.apache.kafka.streams.kstream"><code>KTable</code></a> changelog stream. |
| <p> |
| The specified <a href="../../../../../org/apache/kafka/streams/kstream/Reducer.html" title="interface in org.apache.kafka.streams.kstream"><code>Reducer</code></a> is applied for each input record and computes a new aggregate using the current |
| aggregate (first argument) and the record's value (second argument): |
| <pre><code> |
| // At the example of a Reducer<Long> |
| new Reducer<Long>() { |
| public Long apply(Long aggValue, Long currValue) { |
| return aggValue + currValue; |
| } |
| } |
| </code></pre> |
| <p> |
| If there is no current aggregate the <a href="../../../../../org/apache/kafka/streams/kstream/Reducer.html" title="interface in org.apache.kafka.streams.kstream"><code>Reducer</code></a> is not applied and the new aggregate will be the record's |
| value as-is. |
| Thus, <code>reduce(Reducer, Materialized)</code> can be used to compute aggregate functions like sum, min, or |
| max. |
| <p> |
| Not all updates might get sent downstream, as an internal cache is used to deduplicate consecutive updates to |
| the same key. |
| The rate of propagated updates depends on your input data rate, the number of distinct keys, the number of |
| parallel running Kafka Streams instances, and the <a href="../../../../../org/apache/kafka/streams/StreamsConfig.html" title="class in org.apache.kafka.streams"><code>configuration</code></a> parameters for |
| <a href="../../../../../org/apache/kafka/streams/StreamsConfig.html#CACHE_MAX_BYTES_BUFFERING_CONFIG"><code>cache size</code></a>, and |
| <a href="../../../../../org/apache/kafka/streams/StreamsConfig.html#COMMIT_INTERVAL_MS_CONFIG"><code>commit intervall</code></a>. |
| <p> |
| To query the local <a href="../../../../../org/apache/kafka/streams/state/ReadOnlyKeyValueStore.html" title="interface in org.apache.kafka.streams.state"><code>ReadOnlyKeyValueStore</code></a> it must be obtained via |
| <a href="../../../../../org/apache/kafka/streams/KafkaStreams.html#store-org.apache.kafka.streams.StoreQueryParameters-"><code>KafkaStreams#store(...)</code></a>. |
| <pre><code> |
| KafkaStreams streams = ... // compute sum |
| String queryableStoreName = "storeName" // the store name should be the name of the store as defined by the Materialized instance |
| ReadOnlyKeyValueStore<K, ValueAndTimestamp<V>> localStore = streams.store(queryableStoreName, QueryableStoreTypes.<K, ValueAndTimestamp<V>>timestampedKeyValueStore()); |
| K key = "some-key"; |
| ValueAndTimestamp<V> reduceForKey = localStore.get(key); // key must be local (application state is shared over all running Kafka Streams instances) |
| </code></pre> |
| For non-local keys, a custom RPC mechanism must be implemented using <a href="../../../../../org/apache/kafka/streams/KafkaStreams.html#allMetadata--"><code>KafkaStreams.allMetadata()</code></a> to |
| query the value of the key on a parallel running instance of your Kafka Streams application. |
| |
| <p> |
| For failure and recovery the store will be backed by an internal changelog topic that will be created in Kafka. |
| The changelog topic will be named "${applicationId}-${internalStoreName}-changelog", where "applicationId" is |
| user-specified in <a href="../../../../../org/apache/kafka/streams/StreamsConfig.html" title="class in org.apache.kafka.streams"><code>StreamsConfig</code></a> via parameter |
| <a href="../../../../../org/apache/kafka/streams/StreamsConfig.html#APPLICATION_ID_CONFIG"><code>APPLICATION_ID_CONFIG</code></a>, "internalStoreName" is an internal name |
| and "-changelog" is a fixed suffix. |
| Note that the internal store name may not be queryable through Interactive Queries. |
| |
| You can retrieve all generated internal topic names via <a href="../../../../../org/apache/kafka/streams/Topology.html#describe--"><code>Topology.describe()</code></a>.</div> |
| <dl> |
| <dt><span class="paramLabel">Parameters:</span></dt> |
| <dd><code>reducer</code> - a <a href="../../../../../org/apache/kafka/streams/kstream/Reducer.html" title="interface in org.apache.kafka.streams.kstream"><code>Reducer</code></a> that computes a new aggregate result. Cannot be <code>null</code>.</dd> |
| <dd><code>named</code> - a <a href="../../../../../org/apache/kafka/streams/kstream/Named.html" title="class in org.apache.kafka.streams.kstream"><code>Named</code></a> config used to name the processor in the topology.</dd> |
| <dd><code>materialized</code> - an instance of <a href="../../../../../org/apache/kafka/streams/kstream/Materialized.html" title="class in org.apache.kafka.streams.kstream"><code>Materialized</code></a> used to materialize a state store. Cannot be <code>null</code>.</dd> |
| <dt><span class="returnLabel">Returns:</span></dt> |
| <dd>a <a href="../../../../../org/apache/kafka/streams/kstream/KTable.html" title="interface in org.apache.kafka.streams.kstream"><code>KTable</code></a> that contains "update" records with unmodified keys, and values that represent the |
| latest (rolling) aggregate for each key. If the reduce function returns <code>null</code>, it is then interpreted as |
| deletion for the key, and future messages of the same key coming from upstream operators |
| will be handled as newly initialized value.</dd> |
| </dl> |
| </li> |
| </ul> |
| <a name="aggregate-org.apache.kafka.streams.kstream.Initializer-org.apache.kafka.streams.kstream.Aggregator-"> |
| <!-- --> |
| </a> |
| <ul class="blockList"> |
| <li class="blockList"> |
| <h4>aggregate</h4> |
| <pre><VR> <a href="../../../../../org/apache/kafka/streams/kstream/KTable.html" title="interface in org.apache.kafka.streams.kstream">KTable</a><<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">K</a>,VR> aggregate(<a href="../../../../../org/apache/kafka/streams/kstream/Initializer.html" title="interface in org.apache.kafka.streams.kstream">Initializer</a><VR> initializer, |
| <a href="../../../../../org/apache/kafka/streams/kstream/Aggregator.html" title="interface in org.apache.kafka.streams.kstream">Aggregator</a><? super <a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">K</a>,? super <a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">V</a>,VR> aggregator)</pre> |
| <div class="block">Aggregate the values of records in this stream by the grouped key. |
| Records with <code>null</code> key or value are ignored. |
| Aggregating is a generalization of <a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html#reduce-org.apache.kafka.streams.kstream.Reducer-"><code>combining via reduce(...)</code></a> as it, for example, |
| allows the result to have a different type than the input values. |
| <p> |
| The specified <a href="../../../../../org/apache/kafka/streams/kstream/Initializer.html" title="interface in org.apache.kafka.streams.kstream"><code>Initializer</code></a> is applied once directly before the first input record is processed to |
| provide an initial intermediate aggregation result that is used to process the first record. |
| The specified <a href="../../../../../org/apache/kafka/streams/kstream/Aggregator.html" title="interface in org.apache.kafka.streams.kstream"><code>Aggregator</code></a> is applied for each input record and computes a new aggregate using the current |
| aggregate (or for the very first record using the intermediate aggregation result provided via the |
| <a href="../../../../../org/apache/kafka/streams/kstream/Initializer.html" title="interface in org.apache.kafka.streams.kstream"><code>Initializer</code></a>) and the record's value. |
| Thus, <code>aggregate(Initializer, Aggregator)</code> can be used to compute aggregate functions like |
| count (c.f. <a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html#count--"><code>count()</code></a>). |
| <p> |
| The default value serde from config will be used for serializing the result. |
| If a different serde is required then you should use <a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html#aggregate-org.apache.kafka.streams.kstream.Initializer-org.apache.kafka.streams.kstream.Aggregator-org.apache.kafka.streams.kstream.Materialized-"><code>aggregate(Initializer, Aggregator, Materialized)</code></a>. |
| <p> |
| Not all updates might get sent downstream, as an internal cache is used to deduplicate consecutive updates to |
| the same key. |
| The rate of propagated updates depends on your input data rate, the number of distinct keys, the number of |
| parallel running Kafka Streams instances, and the <a href="../../../../../org/apache/kafka/streams/StreamsConfig.html" title="class in org.apache.kafka.streams"><code>configuration</code></a> parameters for |
| <a href="../../../../../org/apache/kafka/streams/StreamsConfig.html#CACHE_MAX_BYTES_BUFFERING_CONFIG"><code>cache size</code></a>, and |
| <a href="../../../../../org/apache/kafka/streams/StreamsConfig.html#COMMIT_INTERVAL_MS_CONFIG"><code>commit intervall</code></a>. |
| |
| <p> |
| For failure and recovery the store will be backed by an internal changelog topic that will be created in Kafka. |
| The changelog topic will be named "${applicationId}-${internalStoreName}-changelog", where "applicationId" is |
| user-specified in <a href="../../../../../org/apache/kafka/streams/StreamsConfig.html" title="class in org.apache.kafka.streams"><code>StreamsConfig</code></a> via parameter |
| <a href="../../../../../org/apache/kafka/streams/StreamsConfig.html#APPLICATION_ID_CONFIG"><code>APPLICATION_ID_CONFIG</code></a>, "internalStoreName" is an internal name |
| and "-changelog" is a fixed suffix. |
| Note that the internal store name may not be queryable through Interactive Queries. |
| |
| You can retrieve all generated internal topic names via <a href="../../../../../org/apache/kafka/streams/Topology.html#describe--"><code>Topology.describe()</code></a>.</div> |
| <dl> |
| <dt><span class="paramLabel">Type Parameters:</span></dt> |
| <dd><code>VR</code> - the value type of the resulting <a href="../../../../../org/apache/kafka/streams/kstream/KTable.html" title="interface in org.apache.kafka.streams.kstream"><code>KTable</code></a></dd> |
| <dt><span class="paramLabel">Parameters:</span></dt> |
| <dd><code>initializer</code> - an <a href="../../../../../org/apache/kafka/streams/kstream/Initializer.html" title="interface in org.apache.kafka.streams.kstream"><code>Initializer</code></a> that computes an initial intermediate aggregation result</dd> |
| <dd><code>aggregator</code> - an <a href="../../../../../org/apache/kafka/streams/kstream/Aggregator.html" title="interface in org.apache.kafka.streams.kstream"><code>Aggregator</code></a> that computes a new aggregate result</dd> |
| <dt><span class="returnLabel">Returns:</span></dt> |
| <dd>a <a href="../../../../../org/apache/kafka/streams/kstream/KTable.html" title="interface in org.apache.kafka.streams.kstream"><code>KTable</code></a> that contains "update" records with unmodified keys, and values that represent the |
| latest (rolling) aggregate for each key. If the aggregate function returns <code>null</code>, it is then interpreted as |
| deletion for the key, and future messages of the same key coming from upstream operators |
| will be handled as newly initialized value.</dd> |
| </dl> |
| </li> |
| </ul> |
| <a name="aggregate-org.apache.kafka.streams.kstream.Initializer-org.apache.kafka.streams.kstream.Aggregator-org.apache.kafka.streams.kstream.Materialized-"> |
| <!-- --> |
| </a> |
| <ul class="blockList"> |
| <li class="blockList"> |
| <h4>aggregate</h4> |
| <pre><VR> <a href="../../../../../org/apache/kafka/streams/kstream/KTable.html" title="interface in org.apache.kafka.streams.kstream">KTable</a><<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">K</a>,VR> aggregate(<a href="../../../../../org/apache/kafka/streams/kstream/Initializer.html" title="interface in org.apache.kafka.streams.kstream">Initializer</a><VR> initializer, |
| <a href="../../../../../org/apache/kafka/streams/kstream/Aggregator.html" title="interface in org.apache.kafka.streams.kstream">Aggregator</a><? super <a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">K</a>,? super <a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">V</a>,VR> aggregator, |
| <a href="../../../../../org/apache/kafka/streams/kstream/Materialized.html" title="class in org.apache.kafka.streams.kstream">Materialized</a><<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">K</a>,VR,<a href="../../../../../org/apache/kafka/streams/state/KeyValueStore.html" title="interface in org.apache.kafka.streams.state">KeyValueStore</a><org.apache.kafka.common.utils.Bytes,byte[]>> materialized)</pre> |
| <div class="block">Aggregate the values of records in this stream by the grouped key. |
| Records with <code>null</code> key or value are ignored. |
| Aggregating is a generalization of <a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html#reduce-org.apache.kafka.streams.kstream.Reducer-"><code>combining via reduce(...)</code></a> as it, for example, |
| allows the result to have a different type than the input values. |
| The result is written into a local <a href="../../../../../org/apache/kafka/streams/state/KeyValueStore.html" title="interface in org.apache.kafka.streams.state"><code>KeyValueStore</code></a> (which is basically an ever-updating materialized view) |
| that can be queried by the given store name in <code>materialized</code>. |
| Furthermore, updates to the store are sent downstream into a <a href="../../../../../org/apache/kafka/streams/kstream/KTable.html" title="interface in org.apache.kafka.streams.kstream"><code>KTable</code></a> changelog stream. |
| <p> |
| The specified <a href="../../../../../org/apache/kafka/streams/kstream/Initializer.html" title="interface in org.apache.kafka.streams.kstream"><code>Initializer</code></a> is applied once directly before the first input record is processed to |
| provide an initial intermediate aggregation result that is used to process the first record. |
| The specified <a href="../../../../../org/apache/kafka/streams/kstream/Aggregator.html" title="interface in org.apache.kafka.streams.kstream"><code>Aggregator</code></a> is applied for each input record and computes a new aggregate using the current |
| aggregate (or for the very first record using the intermediate aggregation result provided via the |
| <a href="../../../../../org/apache/kafka/streams/kstream/Initializer.html" title="interface in org.apache.kafka.streams.kstream"><code>Initializer</code></a>) and the record's value. |
| Thus, <code>aggregate(Initializer, Aggregator, Materialized)</code> can be used to compute aggregate functions like |
| count (c.f. <a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html#count--"><code>count()</code></a>). |
| <p> |
| Not all updates might get sent downstream, as an internal cache is used to deduplicate consecutive updates to |
| the same key. |
| The rate of propagated updates depends on your input data rate, the number of distinct keys, the number of |
| parallel running Kafka Streams instances, and the <a href="../../../../../org/apache/kafka/streams/StreamsConfig.html" title="class in org.apache.kafka.streams"><code>configuration</code></a> parameters for |
| <a href="../../../../../org/apache/kafka/streams/StreamsConfig.html#CACHE_MAX_BYTES_BUFFERING_CONFIG"><code>cache size</code></a>, and |
| <a href="../../../../../org/apache/kafka/streams/StreamsConfig.html#COMMIT_INTERVAL_MS_CONFIG"><code>commit intervall</code></a>. |
| <p> |
| To query the local <a href="../../../../../org/apache/kafka/streams/state/ReadOnlyKeyValueStore.html" title="interface in org.apache.kafka.streams.state"><code>ReadOnlyKeyValueStore</code></a> it must be obtained via |
| <a href="../../../../../org/apache/kafka/streams/KafkaStreams.html#store-org.apache.kafka.streams.StoreQueryParameters-"><code>KafkaStreams#store(...)</code></a>: |
| <pre><code> |
| KafkaStreams streams = ... // some aggregation on value type double |
| String queryableStoreName = "storeName" // the store name should be the name of the store as defined by the Materialized instance |
| ReadOnlyKeyValueStore<K, ValueAndTimestamp<VR>> localStore = streams.store(queryableStoreName, QueryableStoreTypes.<K, ValueAndTimestamp<VR>>timestampedKeyValueStore()); |
| K key = "some-key"; |
| ValueAndTimestamp<VR> aggForKey = localStore.get(key); // key must be local (application state is shared over all running Kafka Streams instances) |
| </code></pre> |
| For non-local keys, a custom RPC mechanism must be implemented using <a href="../../../../../org/apache/kafka/streams/KafkaStreams.html#allMetadata--"><code>KafkaStreams.allMetadata()</code></a> to |
| query the value of the key on a parallel running instance of your Kafka Streams application. |
| |
| <p> |
| For failure and recovery the store will be backed by an internal changelog topic that will be created in Kafka. |
| Therefore, the store name defined by the Materialized instance must be a valid Kafka topic name and cannot contain characters other than ASCII |
| alphanumerics, '.', '_' and '-'. |
| The changelog topic will be named "${applicationId}-${storeName}-changelog", where "applicationId" is |
| user-specified in <a href="../../../../../org/apache/kafka/streams/StreamsConfig.html" title="class in org.apache.kafka.streams"><code>StreamsConfig</code></a> via parameter |
| <a href="../../../../../org/apache/kafka/streams/StreamsConfig.html#APPLICATION_ID_CONFIG"><code>APPLICATION_ID_CONFIG</code></a>, "storeName" is the |
| provide store name defined in <code>Materialized</code>, and "-changelog" is a fixed suffix. |
| |
| You can retrieve all generated internal topic names via <a href="../../../../../org/apache/kafka/streams/Topology.html#describe--"><code>Topology.describe()</code></a>.</div> |
| <dl> |
| <dt><span class="paramLabel">Type Parameters:</span></dt> |
| <dd><code>VR</code> - the value type of the resulting <a href="../../../../../org/apache/kafka/streams/kstream/KTable.html" title="interface in org.apache.kafka.streams.kstream"><code>KTable</code></a></dd> |
| <dt><span class="paramLabel">Parameters:</span></dt> |
| <dd><code>initializer</code> - an <a href="../../../../../org/apache/kafka/streams/kstream/Initializer.html" title="interface in org.apache.kafka.streams.kstream"><code>Initializer</code></a> that computes an initial intermediate aggregation result</dd> |
| <dd><code>aggregator</code> - an <a href="../../../../../org/apache/kafka/streams/kstream/Aggregator.html" title="interface in org.apache.kafka.streams.kstream"><code>Aggregator</code></a> that computes a new aggregate result</dd> |
| <dd><code>materialized</code> - an instance of <a href="../../../../../org/apache/kafka/streams/kstream/Materialized.html" title="class in org.apache.kafka.streams.kstream"><code>Materialized</code></a> used to materialize a state store. Cannot be <code>null</code>.</dd> |
| <dt><span class="returnLabel">Returns:</span></dt> |
| <dd>a <a href="../../../../../org/apache/kafka/streams/kstream/KTable.html" title="interface in org.apache.kafka.streams.kstream"><code>KTable</code></a> that contains "update" records with unmodified keys, and values that represent the |
| latest (rolling) aggregate for each key</dd> |
| </dl> |
| </li> |
| </ul> |
| <a name="aggregate-org.apache.kafka.streams.kstream.Initializer-org.apache.kafka.streams.kstream.Aggregator-org.apache.kafka.streams.kstream.Named-org.apache.kafka.streams.kstream.Materialized-"> |
| <!-- --> |
| </a> |
| <ul class="blockList"> |
| <li class="blockList"> |
| <h4>aggregate</h4> |
| <pre><VR> <a href="../../../../../org/apache/kafka/streams/kstream/KTable.html" title="interface in org.apache.kafka.streams.kstream">KTable</a><<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">K</a>,VR> aggregate(<a href="../../../../../org/apache/kafka/streams/kstream/Initializer.html" title="interface in org.apache.kafka.streams.kstream">Initializer</a><VR> initializer, |
| <a href="../../../../../org/apache/kafka/streams/kstream/Aggregator.html" title="interface in org.apache.kafka.streams.kstream">Aggregator</a><? super <a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">K</a>,? super <a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">V</a>,VR> aggregator, |
| <a href="../../../../../org/apache/kafka/streams/kstream/Named.html" title="class in org.apache.kafka.streams.kstream">Named</a> named, |
| <a href="../../../../../org/apache/kafka/streams/kstream/Materialized.html" title="class in org.apache.kafka.streams.kstream">Materialized</a><<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">K</a>,VR,<a href="../../../../../org/apache/kafka/streams/state/KeyValueStore.html" title="interface in org.apache.kafka.streams.state">KeyValueStore</a><org.apache.kafka.common.utils.Bytes,byte[]>> materialized)</pre> |
| <div class="block">Aggregate the values of records in this stream by the grouped key. |
| Records with <code>null</code> key or value are ignored. |
| Aggregating is a generalization of <a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html#reduce-org.apache.kafka.streams.kstream.Reducer-"><code>combining via reduce(...)</code></a> as it, for example, |
| allows the result to have a different type than the input values. |
| The result is written into a local <a href="../../../../../org/apache/kafka/streams/state/KeyValueStore.html" title="interface in org.apache.kafka.streams.state"><code>KeyValueStore</code></a> (which is basically an ever-updating materialized view) |
| that can be queried by the given store name in <code>materialized</code>. |
| Furthermore, updates to the store are sent downstream into a <a href="../../../../../org/apache/kafka/streams/kstream/KTable.html" title="interface in org.apache.kafka.streams.kstream"><code>KTable</code></a> changelog stream. |
| <p> |
| The specified <a href="../../../../../org/apache/kafka/streams/kstream/Initializer.html" title="interface in org.apache.kafka.streams.kstream"><code>Initializer</code></a> is applied once directly before the first input record is processed to |
| provide an initial intermediate aggregation result that is used to process the first record. |
| The specified <a href="../../../../../org/apache/kafka/streams/kstream/Aggregator.html" title="interface in org.apache.kafka.streams.kstream"><code>Aggregator</code></a> is applied for each input record and computes a new aggregate using the current |
| aggregate (or for the very first record using the intermediate aggregation result provided via the |
| <a href="../../../../../org/apache/kafka/streams/kstream/Initializer.html" title="interface in org.apache.kafka.streams.kstream"><code>Initializer</code></a>) and the record's value. |
| Thus, <code>aggregate(Initializer, Aggregator, Materialized)</code> can be used to compute aggregate functions like |
| count (c.f. <a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html#count--"><code>count()</code></a>). |
| <p> |
| Not all updates might get sent downstream, as an internal cache is used to deduplicate consecutive updates to |
| the same key. |
| The rate of propagated updates depends on your input data rate, the number of distinct keys, the number of |
| parallel running Kafka Streams instances, and the <a href="../../../../../org/apache/kafka/streams/StreamsConfig.html" title="class in org.apache.kafka.streams"><code>configuration</code></a> parameters for |
| <a href="../../../../../org/apache/kafka/streams/StreamsConfig.html#CACHE_MAX_BYTES_BUFFERING_CONFIG"><code>cache size</code></a>, and |
| <a href="../../../../../org/apache/kafka/streams/StreamsConfig.html#COMMIT_INTERVAL_MS_CONFIG"><code>commit intervall</code></a>. |
| <p> |
| To query the local <a href="../../../../../org/apache/kafka/streams/state/ReadOnlyKeyValueStore.html" title="interface in org.apache.kafka.streams.state"><code>ReadOnlyKeyValueStore</code></a> it must be obtained via |
| <a href="../../../../../org/apache/kafka/streams/KafkaStreams.html#store-org.apache.kafka.streams.StoreQueryParameters-"><code>KafkaStreams#store(...)</code></a>: |
| <pre><code> |
| KafkaStreams streams = ... // some aggregation on value type double |
| String queryableStoreName = "storeName" // the store name should be the name of the store as defined by the Materialized instance |
| ReadOnlyKeyValueStore<K, ValueAndTimestamp<VR>> localStore = streams.store(queryableStoreName, QueryableStoreTypes.<String, ValueAndTimestamp<VR>>timestampedKeyValueStore()); |
| K key = "some-key"; |
| ValueAndTimestamp<VR> aggForKey = localStore.get(key); // key must be local (application state is shared over all running Kafka Streams instances) |
| </code></pre> |
| For non-local keys, a custom RPC mechanism must be implemented using <a href="../../../../../org/apache/kafka/streams/KafkaStreams.html#allMetadata--"><code>KafkaStreams.allMetadata()</code></a> to |
| query the value of the key on a parallel running instance of your Kafka Streams application. |
| |
| <p> |
| For failure and recovery the store will be backed by an internal changelog topic that will be created in Kafka. |
| Therefore, the store name defined by the Materialized instance must be a valid Kafka topic name and cannot contain characters other than ASCII |
| alphanumerics, '.', '_' and '-'. |
| The changelog topic will be named "${applicationId}-${storeName}-changelog", where "applicationId" is |
| user-specified in <a href="../../../../../org/apache/kafka/streams/StreamsConfig.html" title="class in org.apache.kafka.streams"><code>StreamsConfig</code></a> via parameter |
| <a href="../../../../../org/apache/kafka/streams/StreamsConfig.html#APPLICATION_ID_CONFIG"><code>APPLICATION_ID_CONFIG</code></a>, "storeName" is the |
| provide store name defined in <code>Materialized</code>, and "-changelog" is a fixed suffix. |
| |
| You can retrieve all generated internal topic names via <a href="../../../../../org/apache/kafka/streams/Topology.html#describe--"><code>Topology.describe()</code></a>.</div> |
| <dl> |
| <dt><span class="paramLabel">Type Parameters:</span></dt> |
| <dd><code>VR</code> - the value type of the resulting <a href="../../../../../org/apache/kafka/streams/kstream/KTable.html" title="interface in org.apache.kafka.streams.kstream"><code>KTable</code></a></dd> |
| <dt><span class="paramLabel">Parameters:</span></dt> |
| <dd><code>initializer</code> - an <a href="../../../../../org/apache/kafka/streams/kstream/Initializer.html" title="interface in org.apache.kafka.streams.kstream"><code>Initializer</code></a> that computes an initial intermediate aggregation result</dd> |
| <dd><code>aggregator</code> - an <a href="../../../../../org/apache/kafka/streams/kstream/Aggregator.html" title="interface in org.apache.kafka.streams.kstream"><code>Aggregator</code></a> that computes a new aggregate result</dd> |
| <dd><code>named</code> - a <a href="../../../../../org/apache/kafka/streams/kstream/Named.html" title="class in org.apache.kafka.streams.kstream"><code>Named</code></a> config used to name the processor in the topology</dd> |
| <dd><code>materialized</code> - an instance of <a href="../../../../../org/apache/kafka/streams/kstream/Materialized.html" title="class in org.apache.kafka.streams.kstream"><code>Materialized</code></a> used to materialize a state store. Cannot be <code>null</code>.</dd> |
| <dt><span class="returnLabel">Returns:</span></dt> |
| <dd>a <a href="../../../../../org/apache/kafka/streams/kstream/KTable.html" title="interface in org.apache.kafka.streams.kstream"><code>KTable</code></a> that contains "update" records with unmodified keys, and values that represent the |
| latest (rolling) aggregate for each key. If the aggregate function returns <code>null</code>, it is then interpreted as |
| deletion for the key, and future messages of the same key coming from upstream operators |
| will be handled as newly initialized value.</dd> |
| </dl> |
| </li> |
| </ul> |
| <a name="windowedBy-org.apache.kafka.streams.kstream.Windows-"> |
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| </a> |
| <ul class="blockList"> |
| <li class="blockList"> |
| <h4>windowedBy</h4> |
| <pre><W extends <a href="../../../../../org/apache/kafka/streams/kstream/Window.html" title="class in org.apache.kafka.streams.kstream">Window</a>> <a href="../../../../../org/apache/kafka/streams/kstream/TimeWindowedKStream.html" title="interface in org.apache.kafka.streams.kstream">TimeWindowedKStream</a><<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">K</a>,<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">V</a>> windowedBy(<a href="../../../../../org/apache/kafka/streams/kstream/Windows.html" title="class in org.apache.kafka.streams.kstream">Windows</a><W> windows)</pre> |
| <div class="block">Create a new <a href="../../../../../org/apache/kafka/streams/kstream/TimeWindowedKStream.html" title="interface in org.apache.kafka.streams.kstream"><code>TimeWindowedKStream</code></a> instance that can be used to perform windowed aggregations.</div> |
| <dl> |
| <dt><span class="paramLabel">Type Parameters:</span></dt> |
| <dd><code>W</code> - the window type</dd> |
| <dt><span class="paramLabel">Parameters:</span></dt> |
| <dd><code>windows</code> - the specification of the aggregation <a href="../../../../../org/apache/kafka/streams/kstream/Windows.html" title="class in org.apache.kafka.streams.kstream"><code>Windows</code></a></dd> |
| <dt><span class="returnLabel">Returns:</span></dt> |
| <dd>an instance of <a href="../../../../../org/apache/kafka/streams/kstream/TimeWindowedKStream.html" title="interface in org.apache.kafka.streams.kstream"><code>TimeWindowedKStream</code></a></dd> |
| </dl> |
| </li> |
| </ul> |
| <a name="windowedBy-org.apache.kafka.streams.kstream.SlidingWindows-"> |
| <!-- --> |
| </a> |
| <ul class="blockList"> |
| <li class="blockList"> |
| <h4>windowedBy</h4> |
| <pre><a href="../../../../../org/apache/kafka/streams/kstream/TimeWindowedKStream.html" title="interface in org.apache.kafka.streams.kstream">TimeWindowedKStream</a><<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">K</a>,<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">V</a>> windowedBy(<a href="../../../../../org/apache/kafka/streams/kstream/SlidingWindows.html" title="class in org.apache.kafka.streams.kstream">SlidingWindows</a> windows)</pre> |
| <div class="block">Create a new <a href="../../../../../org/apache/kafka/streams/kstream/TimeWindowedKStream.html" title="interface in org.apache.kafka.streams.kstream"><code>TimeWindowedKStream</code></a> instance that can be used to perform sliding windowed aggregations.</div> |
| <dl> |
| <dt><span class="paramLabel">Parameters:</span></dt> |
| <dd><code>windows</code> - the specification of the aggregation <a href="../../../../../org/apache/kafka/streams/kstream/SlidingWindows.html" title="class in org.apache.kafka.streams.kstream"><code>SlidingWindows</code></a></dd> |
| <dt><span class="returnLabel">Returns:</span></dt> |
| <dd>an instance of <a href="../../../../../org/apache/kafka/streams/kstream/TimeWindowedKStream.html" title="interface in org.apache.kafka.streams.kstream"><code>TimeWindowedKStream</code></a></dd> |
| </dl> |
| </li> |
| </ul> |
| <a name="windowedBy-org.apache.kafka.streams.kstream.SessionWindows-"> |
| <!-- --> |
| </a> |
| <ul class="blockList"> |
| <li class="blockList"> |
| <h4>windowedBy</h4> |
| <pre><a href="../../../../../org/apache/kafka/streams/kstream/SessionWindowedKStream.html" title="interface in org.apache.kafka.streams.kstream">SessionWindowedKStream</a><<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">K</a>,<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">V</a>> windowedBy(<a href="../../../../../org/apache/kafka/streams/kstream/SessionWindows.html" title="class in org.apache.kafka.streams.kstream">SessionWindows</a> windows)</pre> |
| <div class="block">Create a new <a href="../../../../../org/apache/kafka/streams/kstream/SessionWindowedKStream.html" title="interface in org.apache.kafka.streams.kstream"><code>SessionWindowedKStream</code></a> instance that can be used to perform session windowed aggregations.</div> |
| <dl> |
| <dt><span class="paramLabel">Parameters:</span></dt> |
| <dd><code>windows</code> - the specification of the aggregation <a href="../../../../../org/apache/kafka/streams/kstream/SessionWindows.html" title="class in org.apache.kafka.streams.kstream"><code>SessionWindows</code></a></dd> |
| <dt><span class="returnLabel">Returns:</span></dt> |
| <dd>an instance of <a href="../../../../../org/apache/kafka/streams/kstream/TimeWindowedKStream.html" title="interface in org.apache.kafka.streams.kstream"><code>TimeWindowedKStream</code></a></dd> |
| </dl> |
| </li> |
| </ul> |
| <a name="cogroup-org.apache.kafka.streams.kstream.Aggregator-"> |
| <!-- --> |
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| <ul class="blockListLast"> |
| <li class="blockList"> |
| <h4>cogroup</h4> |
| <pre><VOut> <a href="../../../../../org/apache/kafka/streams/kstream/CogroupedKStream.html" title="interface in org.apache.kafka.streams.kstream">CogroupedKStream</a><<a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">K</a>,VOut> cogroup(<a href="../../../../../org/apache/kafka/streams/kstream/Aggregator.html" title="interface in org.apache.kafka.streams.kstream">Aggregator</a><? super <a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">K</a>,? super <a href="../../../../../org/apache/kafka/streams/kstream/KGroupedStream.html" title="type parameter in KGroupedStream">V</a>,VOut> aggregator)</pre> |
| <div class="block">Create a new <a href="../../../../../org/apache/kafka/streams/kstream/CogroupedKStream.html" title="interface in org.apache.kafka.streams.kstream"><code>CogroupedKStream</code></a> from the this grouped KStream to allow cogrouping other |
| <code>KGroupedStream</code> to it. |
| <a href="../../../../../org/apache/kafka/streams/kstream/CogroupedKStream.html" title="interface in org.apache.kafka.streams.kstream"><code>CogroupedKStream</code></a> is an abstraction of multiple <i>grouped</i> record streams of <a href="../../../../../org/apache/kafka/streams/KeyValue.html" title="class in org.apache.kafka.streams"><code>KeyValue</code></a> pairs. |
| It is an intermediate representation after a grouping of <a href="../../../../../org/apache/kafka/streams/kstream/KStream.html" title="interface in org.apache.kafka.streams.kstream"><code>KStream</code></a>s, before the |
| aggregations are applied to the new partitions resulting in a <a href="../../../../../org/apache/kafka/streams/kstream/KTable.html" title="interface in org.apache.kafka.streams.kstream"><code>KTable</code></a>. |
| <p> |
| The specified <a href="../../../../../org/apache/kafka/streams/kstream/Aggregator.html" title="interface in org.apache.kafka.streams.kstream"><code>Aggregator</code></a> is applied in the actual <a href="../../../../../org/apache/kafka/streams/kstream/CogroupedKStream.html#aggregate-org.apache.kafka.streams.kstream.Initializer-"><code>aggregation</code></a> step for each input record and computes a new aggregate using the current aggregate (or for the very |
| first record per key using the initial intermediate aggregation result provided via the <a href="../../../../../org/apache/kafka/streams/kstream/Initializer.html" title="interface in org.apache.kafka.streams.kstream"><code>Initializer</code></a> that |
| is passed into <a href="../../../../../org/apache/kafka/streams/kstream/CogroupedKStream.html#aggregate-org.apache.kafka.streams.kstream.Initializer-"><code>CogroupedKStream.aggregate(Initializer)</code></a>) and the record's value.</div> |
| <dl> |
| <dt><span class="paramLabel">Type Parameters:</span></dt> |
| <dd><code>VOut</code> - the type of the output values</dd> |
| <dt><span class="paramLabel">Parameters:</span></dt> |
| <dd><code>aggregator</code> - an <a href="../../../../../org/apache/kafka/streams/kstream/Aggregator.html" title="interface in org.apache.kafka.streams.kstream"><code>Aggregator</code></a> that computes a new aggregate result</dd> |
| <dt><span class="returnLabel">Returns:</span></dt> |
| <dd>a <a href="../../../../../org/apache/kafka/streams/kstream/CogroupedKStream.html" title="interface in org.apache.kafka.streams.kstream"><code>CogroupedKStream</code></a></dd> |
| </dl> |
| </li> |
| </ul> |
| </li> |
| </ul> |
| </li> |
| </ul> |
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