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| <div class="subTitle">org.apache.beam.sdk.io.contextualtextio</div> |
| <h2 title="Class ContextualTextIO" class="title">Class ContextualTextIO</h2> |
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| <ul class="inheritance"> |
| <li>java.lang.Object</li> |
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| <li>org.apache.beam.sdk.io.contextualtextio.ContextualTextIO</li> |
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| <pre>public class <span class="typeNameLabel">ContextualTextIO</span> |
| extends java.lang.Object</pre> |
| <div class="block"><a href="../../../../../../org/apache/beam/sdk/transforms/PTransform.html" title="class in org.apache.beam.sdk.transforms"><code>PTransform</code></a>s that read text files and collect contextual information of the elements in |
| the input. |
| |
| <p>Prefer <a href="../../../../../../org/apache/beam/sdk/io/TextIO.html" title="class in org.apache.beam.sdk.io"><code>TextIO</code></a> when not reading files with multi-line records or additional record |
| metadata is not required. |
| |
| <h2>Reading from text files</h2> |
| |
| <p>To read a <a href="../../../../../../org/apache/beam/sdk/values/PCollection.html" title="class in org.apache.beam.sdk.values"><code>PCollection</code></a> from one or more text files, use <code>ContextualTextIO.read()</code>. To instantiate a transform use <a href="../../../../../../org/apache/beam/sdk/io/contextualtextio/ContextualTextIO.Read.html#from-java.lang.String-"><code>ContextualTextIO.Read.from(String)</code></a> and specify the path of the file(s) to be read. |
| Alternatively, if the filenames to be read are themselves in a <a href="../../../../../../org/apache/beam/sdk/values/PCollection.html" title="class in org.apache.beam.sdk.values"><code>PCollection</code></a> you can use |
| <a href="../../../../../../org/apache/beam/sdk/io/FileIO.html" title="class in org.apache.beam.sdk.io"><code>FileIO</code></a> to match them and <a href="../../../../../../org/apache/beam/sdk/io/contextualtextio/ContextualTextIO.html#readFiles--"><code>readFiles()</code></a> to read them. |
| |
| <p><a href="../../../../../../org/apache/beam/sdk/io/contextualtextio/ContextualTextIO.html#read--"><code>read()</code></a> returns a <a href="../../../../../../org/apache/beam/sdk/values/PCollection.html" title="class in org.apache.beam.sdk.values"><code>PCollection</code></a> of <a href="../../../../../../org/apache/beam/sdk/values/Row.html" title="class in org.apache.beam.sdk.values"><code>Row</code></a>s with schema <a href="../../../../../../org/apache/beam/sdk/io/contextualtextio/RecordWithMetadata.html#getSchema--"><code>RecordWithMetadata.getSchema()</code></a>, each corresponding to one line of an input UTF-8 text file |
| (split into lines delimited by '\n', '\r', '\r\n', or specified delimiter via <a href="../../../../../../org/apache/beam/sdk/io/contextualtextio/ContextualTextIO.Read.html#withDelimiter-byte:A-"><code>ContextualTextIO.Read.withDelimiter(byte[])</code></a>). |
| |
| <h3>Filepattern expansion and watching</h3> |
| |
| <p>By default, the filepatterns are expanded only once. The combination of <code>FileIO.Match#continuously(Duration, TerminationCondition)</code> and <a href="../../../../../../org/apache/beam/sdk/io/contextualtextio/ContextualTextIO.html#readFiles--"><code>readFiles()</code></a> allow |
| streaming of new files matching the filepattern(s). |
| |
| <p>By default, <a href="../../../../../../org/apache/beam/sdk/io/contextualtextio/ContextualTextIO.html#read--"><code>read()</code></a> prohibits filepatterns that match no files, and <a href="../../../../../../org/apache/beam/sdk/io/contextualtextio/ContextualTextIO.html#readFiles--"><code>readFiles()</code></a> |
| allows them in case the filepattern contains a glob wildcard character. Use <a href="../../../../../../org/apache/beam/sdk/io/contextualtextio/ContextualTextIO.Read.html#withEmptyMatchTreatment-org.apache.beam.sdk.io.fs.EmptyMatchTreatment-"><code>ContextualTextIO.Read.withEmptyMatchTreatment(org.apache.beam.sdk.io.fs.EmptyMatchTreatment)</code></a> or <code>FileIO.Match#withEmptyMatchTreatment(EmptyMatchTreatment)</code> plus <a href="../../../../../../org/apache/beam/sdk/io/contextualtextio/ContextualTextIO.html#readFiles--"><code>readFiles()</code></a> to configure |
| this behavior. |
| |
| <p>Example 1: reading a file or filepattern. |
| |
| <pre><code> |
| Pipeline p = ...; |
| |
| // A simple Read of a file: |
| PCollection<Row> records = p.apply(ContextualTextIO.read().from("/local/path/to/file.txt")); |
| </code></pre> |
| |
| <p>Example 2: reading a PCollection of filenames. |
| |
| <pre><code> |
| Pipeline p = ...; |
| |
| // E.g. the filenames might be computed from other data in the pipeline, or |
| // read from a data source. |
| PCollection<String> filenames = ...; |
| |
| // Read all files in the collection. |
| PCollection<Row> records = |
| filenames |
| .apply(FileIO.matchAll()) |
| .apply(FileIO.readMatches()) |
| .apply(ContextualTextIO.readFiles()); |
| </code></pre> |
| |
| <p>Example 3: streaming new files matching a filepattern. |
| |
| <pre><code> |
| Pipeline p = ...; |
| |
| PCollection<Row> records = p.apply(ContextualTextIO.read() |
| .from("/local/path/to/files/*") |
| .watchForNewFiles( |
| // Check for new files every minute |
| Duration.standardMinutes(1), |
| // Stop watching the filepattern if no new files appear within an hour |
| afterTimeSinceNewOutput(Duration.standardHours(1)))); |
| </code></pre> |
| |
| <p>Example 4: reading a file or file pattern of RFC4180-compliant CSV files with fields that may |
| contain line breaks. |
| |
| <p>Example of such a file could be: |
| |
| <p>"aaa","b CRLF bb","ccc" CRLF zzz,yyy,xxx |
| |
| <pre><code> |
| Pipeline p = ...; |
| |
| PCollection<Row> records = p.apply(ContextualTextIO.read() |
| .from("/local/path/to/files/*.csv") |
| .withHasMultilineCSVRecords(true)); |
| </code></pre> |
| |
| <p>Example 5: reading while watching for new files |
| |
| <pre><code> |
| Pipeline p = ...; |
| |
| PCollection<Row> records = p.apply(FileIO.match() |
| .filepattern("filepattern") |
| .continuously( |
| Duration.millis(100), |
| Watch.Growth.afterTimeSinceNewOutput(Duration.standardSeconds(3)))) |
| .apply(FileIO.readMatches()) |
| .apply(ContextualTextIO.readFiles()); |
| </code></pre> |
| |
| <p>Example 6: reading with recordNum metadata. |
| |
| <pre><code> |
| Pipeline p = ...; |
| |
| PCollection<Row> records = p.apply(ContextualTextIO.read() |
| .from("/local/path/to/files/*.csv") |
| .setWithRecordNumMetadata(true)); |
| </code></pre> |
| |
| <p>NOTE: When using <a href="../../../../../../org/apache/beam/sdk/io/contextualtextio/ContextualTextIO.Read.html#withHasMultilineCSVRecords-java.lang.Boolean-"><code>ContextualTextIO.Read.withHasMultilineCSVRecords(Boolean)</code></a>, a single |
| reader will be used to process the file, rather than multiple readers which can read from |
| different offsets. For a large file this can result in lower performance. |
| |
| <p>NOTE: Use <a href="../../../../../../org/apache/beam/sdk/io/contextualtextio/ContextualTextIO.Read.html#withRecordNumMetadata--"><code>ContextualTextIO.Read.withRecordNumMetadata()</code></a> when recordNum metadata is required. Computing |
| absolute record positions currently introduces a grouping step, which increases the resources |
| used by the pipeline. By default withRecordNumMetadata is set to false, in this case record |
| objects will not contain absolute record positions within the entire file, but will still contain |
| relative positions in respective offsets. |
| |
| <h3>Reading a very large number of files</h3> |
| |
| <p>If it is known that the filepattern will match a very large number of files (e.g. tens of |
| thousands or more), use <a href="../../../../../../org/apache/beam/sdk/io/contextualtextio/ContextualTextIO.Read.html#withHintMatchesManyFiles--"><code>ContextualTextIO.Read.withHintMatchesManyFiles()</code></a> for better |
| performance and scalability. Note that it may decrease performance if the filepattern matches |
| only a small number of files.</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/contextualtextio/ContextualTextIO.Read.html" title="class in org.apache.beam.sdk.io.contextualtextio">ContextualTextIO.Read</a></span></code> |
| <div class="block">Implementation of <a href="../../../../../../org/apache/beam/sdk/io/contextualtextio/ContextualTextIO.html#read--"><code>read()</code></a>.</div> |
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| <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/contextualtextio/ContextualTextIO.ReadFiles.html" title="class in org.apache.beam.sdk.io.contextualtextio">ContextualTextIO.ReadFiles</a></span></code> |
| <div class="block">Implementation of <a href="../../../../../../org/apache/beam/sdk/io/contextualtextio/ContextualTextIO.html#readFiles--"><code>readFiles()</code></a>.</div> |
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| <td class="colFirst"><code>static <a href="../../../../../../org/apache/beam/sdk/io/contextualtextio/ContextualTextIO.Read.html" title="class in org.apache.beam.sdk.io.contextualtextio">ContextualTextIO.Read</a></code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../../org/apache/beam/sdk/io/contextualtextio/ContextualTextIO.html#read--">read</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 one or more text files and returns a bounded <a href="../../../../../../org/apache/beam/sdk/values/PCollection.html" title="class in org.apache.beam.sdk.values"><code>PCollection</code></a> containing one <a href="../../../../../../org/apache/beam/sdk/values/Row.html" title="class in org.apache.beam.sdk.values"><code>element</code></a> for each line in the input files.</div> |
| </td> |
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| <tr id="i1" class="rowColor"> |
| <td class="colFirst"><code>static <a href="../../../../../../org/apache/beam/sdk/io/contextualtextio/ContextualTextIO.ReadFiles.html" title="class in org.apache.beam.sdk.io.contextualtextio">ContextualTextIO.ReadFiles</a></code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../../org/apache/beam/sdk/io/contextualtextio/ContextualTextIO.html#readFiles--">readFiles</a></span>()</code> |
| <div class="block">Like <a href="../../../../../../org/apache/beam/sdk/io/contextualtextio/ContextualTextIO.html#read--"><code>read()</code></a>, but reads each file in a <a href="../../../../../../org/apache/beam/sdk/values/PCollection.html" title="class in org.apache.beam.sdk.values"><code>PCollection</code></a> of <code>FileIO.ReadableFile</code>, returned by <a href="../../../../../../org/apache/beam/sdk/io/FileIO.html#readMatches--"><code>FileIO.readMatches()</code></a>.</div> |
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| <pre>public static <a href="../../../../../../org/apache/beam/sdk/io/contextualtextio/ContextualTextIO.Read.html" title="class in org.apache.beam.sdk.io.contextualtextio">ContextualTextIO.Read</a> read()</pre> |
| <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 one or more text files and returns a bounded <a href="../../../../../../org/apache/beam/sdk/values/PCollection.html" title="class in org.apache.beam.sdk.values"><code>PCollection</code></a> containing one <a href="../../../../../../org/apache/beam/sdk/values/Row.html" title="class in org.apache.beam.sdk.values"><code>element</code></a> for each line in the input files.</div> |
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| <pre>public static <a href="../../../../../../org/apache/beam/sdk/io/contextualtextio/ContextualTextIO.ReadFiles.html" title="class in org.apache.beam.sdk.io.contextualtextio">ContextualTextIO.ReadFiles</a> readFiles()</pre> |
| <div class="block">Like <a href="../../../../../../org/apache/beam/sdk/io/contextualtextio/ContextualTextIO.html#read--"><code>read()</code></a>, but reads each file in a <a href="../../../../../../org/apache/beam/sdk/values/PCollection.html" title="class in org.apache.beam.sdk.values"><code>PCollection</code></a> of <code>FileIO.ReadableFile</code>, returned by <a href="../../../../../../org/apache/beam/sdk/io/FileIO.html#readMatches--"><code>FileIO.readMatches()</code></a>.</div> |
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