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| <div class="subTitle">org.apache.beam.sdk.io.hadoop.inputformat</div> |
| <h2 title="Class HadoopInputFormatIO" class="title">Class HadoopInputFormatIO</h2> |
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| <ul class="inheritance"> |
| <li>java.lang.Object</li> |
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| <li>org.apache.beam.sdk.io.hadoop.inputformat.HadoopInputFormatIO</li> |
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| <pre><a href="../../../../../../../org/apache/beam/sdk/annotations/Experimental.html" title="annotation in org.apache.beam.sdk.annotations">@Experimental</a>(<a href="../../../../../../../org/apache/beam/sdk/annotations/Experimental.html#value--">value</a>=<a href="../../../../../../../org/apache/beam/sdk/annotations/Experimental.Kind.html#SOURCE_SINK">SOURCE_SINK</a>) |
| public class <span class="typeNameLabel">HadoopInputFormatIO</span> |
| extends java.lang.Object</pre> |
| <div class="block">A <a href="../../../../../../../org/apache/beam/sdk/io/hadoop/inputformat/HadoopInputFormatIO.html" title="class in org.apache.beam.sdk.io.hadoop.inputformat"><code>HadoopInputFormatIO</code></a> is a Transform for reading data from any source which implements |
| Hadoop <code>InputFormat</code>. For example- Cassandra, Elasticsearch, HBase, Redis, Postgres etc. |
| <a href="../../../../../../../org/apache/beam/sdk/io/hadoop/inputformat/HadoopInputFormatIO.html" title="class in org.apache.beam.sdk.io.hadoop.inputformat"><code>HadoopInputFormatIO</code></a> has to make several performance trade-offs in connecting to <code>InputFormat</code>, so if there is another Beam IO Transform specifically for connecting to your data |
| source of choice, we would recommend using that one, but this IO Transform allows you to connect |
| to many data sources that do not yet have a Beam IO Transform. |
| |
| <p>You will need to pass a Hadoop <code>Configuration</code> with parameters specifying how the read |
| will occur. Many properties of the Configuration are optional, and some are required for certain |
| <code>InputFormat</code> classes, but the following properties must be set for all InputFormats: |
| |
| <ul> |
| <li><code>mapreduce.job.inputformat.class</code>: The <code>InputFormat</code> class used to connect to |
| your data source of choice. |
| <li><code>key.class</code>: The key class returned by the <code>InputFormat</code> in <code>mapreduce.job.inputformat.class</code>. |
| <li><code>value.class</code>: The value class returned by the <code>InputFormat</code> in <code>mapreduce.job.inputformat.class</code>. |
| </ul> |
| |
| For example: |
| |
| <pre> |
| { |
| Configuration myHadoopConfiguration = new Configuration(false); |
| // Set Hadoop InputFormat, key and value class in configuration |
| myHadoopConfiguration.setClass("mapreduce.job.inputformat.class", |
| MyDbInputFormatClass, InputFormat.class); |
| myHadoopConfiguration.setClass("key.class", MyDbInputFormatKeyClass, Object.class); |
| myHadoopConfiguration.setClass("value.class", |
| MyDbInputFormatValueClass, Object.class); |
| } |
| </pre> |
| |
| <p>You will need to check to see if the key and value classes output by the <code>InputFormat</code> |
| have a Beam <a href="../../../../../../../org/apache/beam/sdk/coders/Coder.html" title="class in org.apache.beam.sdk.coders"><code>Coder</code></a> available. If not, you can use withKeyTranslation/withValueTranslation |
| to specify a method transforming instances of those classes into another class that is supported |
| by a Beam <a href="../../../../../../../org/apache/beam/sdk/coders/Coder.html" title="class in org.apache.beam.sdk.coders"><code>Coder</code></a>. These settings are optional and you don't need to specify translation |
| for both key and value. If you specify a translation, you will need to make sure the K or V of |
| the read transform match the output type of the translation. |
| |
| <p>You will need to set appropriate InputFormat key and value class (i.e. "key.class" and |
| "value.class") in Hadoop <code>Configuration</code>. If you set different InputFormat key or value |
| class than InputFormat's actual key or value class then, it may result in an error like |
| "unexpected extra bytes after decoding" while the decoding process of key/value object happens. |
| Hence, it is important to set appropriate InputFormat key and value class. |
| |
| <h3>Reading using <a href="../../../../../../../org/apache/beam/sdk/io/hadoop/inputformat/HadoopInputFormatIO.html" title="class in org.apache.beam.sdk.io.hadoop.inputformat"><code>HadoopInputFormatIO</code></a></h3> |
| |
| <pre><code> |
| Pipeline p = ...; // Create pipeline. |
| // Read data only with Hadoop configuration. |
| p.apply("read", |
| HadoopInputFormatIO.<InputFormatKeyClass, InputFormatKeyClass>read() |
| .withConfiguration(myHadoopConfiguration); |
| </code> |
| // Read data with configuration and key translation (Example scenario: Beam Coder is not |
| available for key class hence key translation is required.). |
| SimpleFunction<InputFormatKeyClass, MyKeyClass> myOutputKeyType = |
| new SimpleFunction<InputFormatKeyClass, MyKeyClass>() { |
| public MyKeyClass apply(InputFormatKeyClass input) { |
| // ...logic to transform InputFormatKeyClass to MyKeyClass |
| } |
| }; |
| </pre> |
| |
| <pre><code> |
| p.apply("read", |
| HadoopInputFormatIO.<MyKeyClass, InputFormatKeyClass>read() |
| .withConfiguration(myHadoopConfiguration) |
| .withKeyTranslation(myOutputKeyType); |
| </code></pre> |
| |
| <p>// Read data with configuration and value translation (Example scenario: Beam Coder is not |
| available for value class hence value translation is required.). |
| |
| <pre><code> |
| SimpleFunction&lt;InputFormatValueClass, MyValueClass&gt; myOutputValueType = |
| new SimpleFunction&lt;InputFormatValueClass, MyValueClass&gt;() { |
| public MyValueClass apply(InputFormatValueClass input) { |
| // ...logic to transform InputFormatValueClass to MyValueClass |
| } |
| }; |
| </code></pre> |
| |
| <pre><code> |
| p.apply("read", |
| HadoopInputFormatIO.<InputFormatKeyClass, MyValueClass>read() |
| .withConfiguration(myHadoopConfiguration) |
| .withValueTranslation(myOutputValueType); |
| </code></pre> |
| |
| <p>IMPORTANT! In case of using <code>DBInputFormat</code> to read data from RDBMS, Beam parallelizes |
| the process by using LIMIT and OFFSET clauses of SQL query to fetch different ranges of records |
| (as a split) by different workers. To guarantee the same order and proper split of results you |
| need to order them by one or more keys (either PRIMARY or UNIQUE). It can be done during |
| configuration step, for example: |
| |
| <pre><code> |
| Configuration conf = new Configuration(); |
| conf.set(DBConfiguration.INPUT_TABLE_NAME_PROPERTY, tableName); |
| conf.setStrings(DBConfiguration.INPUT_FIELD_NAMES_PROPERTY, "id", "name"); |
| conf.set(DBConfiguration.INPUT_ORDER_BY_PROPERTY, "id ASC"); |
| </code></pre></div> |
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| <td class="colFirst"><code>static class </code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../../../org/apache/beam/sdk/io/hadoop/inputformat/HadoopInputFormatIO.HadoopInputFormatBoundedSource.html" title="class in org.apache.beam.sdk.io.hadoop.inputformat">HadoopInputFormatIO.HadoopInputFormatBoundedSource</a><<a href="../../../../../../../org/apache/beam/sdk/io/hadoop/inputformat/HadoopInputFormatIO.HadoopInputFormatBoundedSource.html" title="type parameter in HadoopInputFormatIO.HadoopInputFormatBoundedSource">K</a>,<a href="../../../../../../../org/apache/beam/sdk/io/hadoop/inputformat/HadoopInputFormatIO.HadoopInputFormatBoundedSource.html" title="type parameter in HadoopInputFormatIO.HadoopInputFormatBoundedSource">V</a>></span></code> |
| <div class="block">Bounded source implementation for <a href="../../../../../../../org/apache/beam/sdk/io/hadoop/inputformat/HadoopInputFormatIO.html" title="class in org.apache.beam.sdk.io.hadoop.inputformat"><code>HadoopInputFormatIO</code></a>.</div> |
| </td> |
| </tr> |
| <tr class="rowColor"> |
| <td class="colFirst"><code>static class </code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../../../org/apache/beam/sdk/io/hadoop/inputformat/HadoopInputFormatIO.Read.html" title="class in org.apache.beam.sdk.io.hadoop.inputformat">HadoopInputFormatIO.Read</a><<a href="../../../../../../../org/apache/beam/sdk/io/hadoop/inputformat/HadoopInputFormatIO.Read.html" title="type parameter in HadoopInputFormatIO.Read">K</a>,<a href="../../../../../../../org/apache/beam/sdk/io/hadoop/inputformat/HadoopInputFormatIO.Read.html" title="type parameter in HadoopInputFormatIO.Read">V</a>></span></code> |
| <div class="block">A <a href="../../../../../../../org/apache/beam/sdk/transforms/PTransform.html" title="class in org.apache.beam.sdk.transforms"><code>PTransform</code></a> that reads from any data source which implements Hadoop InputFormat.</div> |
| </td> |
| </tr> |
| <tr class="altColor"> |
| <td class="colFirst"><code>static class </code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../../../org/apache/beam/sdk/io/hadoop/inputformat/HadoopInputFormatIO.SerializableSplit.html" title="class in org.apache.beam.sdk.io.hadoop.inputformat">HadoopInputFormatIO.SerializableSplit</a></span></code> |
| <div class="block">A wrapper to allow Hadoop <code>InputSplit</code> to be serialized using |
| Java's standard serialization mechanisms.</div> |
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| <td class="colFirst"><code>static <K,V> <a href="../../../../../../../org/apache/beam/sdk/io/hadoop/inputformat/HadoopInputFormatIO.Read.html" title="class in org.apache.beam.sdk.io.hadoop.inputformat">HadoopInputFormatIO.Read</a><K,V></code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../../../org/apache/beam/sdk/io/hadoop/inputformat/HadoopInputFormatIO.html#read--">read</a></span>()</code> |
| <div class="block">Creates an uninitialized <a href="../../../../../../../org/apache/beam/sdk/io/hadoop/inputformat/HadoopInputFormatIO.Read.html" title="class in org.apache.beam.sdk.io.hadoop.inputformat"><code>HadoopInputFormatIO.Read</code></a>.</div> |
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| <pre>public HadoopInputFormatIO()</pre> |
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| <pre>public static <K,V> <a href="../../../../../../../org/apache/beam/sdk/io/hadoop/inputformat/HadoopInputFormatIO.Read.html" title="class in org.apache.beam.sdk.io.hadoop.inputformat">HadoopInputFormatIO.Read</a><K,V> read()</pre> |
| <div class="block">Creates an uninitialized <a href="../../../../../../../org/apache/beam/sdk/io/hadoop/inputformat/HadoopInputFormatIO.Read.html" title="class in org.apache.beam.sdk.io.hadoop.inputformat"><code>HadoopInputFormatIO.Read</code></a>. Before use, the <code>Read</code> must be |
| initialized with a HadoopInputFormatIO.Read#withConfiguration(HadoopConfiguration) that |
| specifies the source. A key/value translation may also optionally be specified using <a href="../../../../../../../org/apache/beam/sdk/io/hadoop/inputformat/HadoopInputFormatIO.Read.html#withKeyTranslation-org.apache.beam.sdk.transforms.SimpleFunction-"><code>HadoopInputFormatIO.Read.withKeyTranslation(org.apache.beam.sdk.transforms.SimpleFunction<?, K>)</code></a>/ <a href="../../../../../../../org/apache/beam/sdk/io/hadoop/inputformat/HadoopInputFormatIO.Read.html#withValueTranslation-org.apache.beam.sdk.transforms.SimpleFunction-"><code>HadoopInputFormatIO.Read.withValueTranslation(org.apache.beam.sdk.transforms.SimpleFunction<?, V>)</code></a>.</div> |
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