[jira] [Commented] (FLINK-834) Extend writeAsText with custom formatting function.

["Chesnay Schepler (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/FLINK-834?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14047125#comment-14047125 ] 

Chesnay Schepler commented on FLINK-834:
----------------------------------------

which version would be more desirable:

implemented as additional map:
{code:java}
public DataSink<String> writeAsFormattedText(String filePath, final TextFormatter<T> txt) {
		return this.map(new MapFunction<T, String>() {			
			@Override
			public String map(T value) throws Exception {
				return txt.format(value);
			}			
		}).writeAsText(filePath);
	}
{code}

implemented in sink:
{code:java}
...
public TextOutputFormat(Path outputPath, TextFormatter txt) {
		this(outputPath, "UTF-8");
		this.formatter = txt;
	}
...
@Override
	public void writeRecord(T record) throws IOException {
		byte[] bytes = this.formatter == null 
				? record.toString().getBytes(charset)
				: formatter.format(record).getBytes(charset);
		this.stream.write(bytes);
		this.stream.write(NEWLINE);
	}
...
{code}

> Extend writeAsText with custom formatting function.
> ---------------------------------------------------
>
>                 Key: FLINK-834
>                 URL: https://issues.apache.org/jira/browse/FLINK-834
>             Project: Flink
>          Issue Type: Improvement
>            Reporter: GitHub Import
>              Labels: github-import, starter
>             Fix For: pre-apache
>
>
> Currently, write as text uses the `toString()` method of data types to serialize the output as text. Alternatively, we have a CSV format that writes Tuple Datasets by using the `toString()` methods of the individual fields. Since Tuple's `toString()` method cannot be adapted without extending the class, it is not easily possible to define a custom output format of data sets which include Tuples.
> I think it would be good to have a way to explicitly format a text output. 
> We could add a formatting function that returns a String for an input element, such as
> ```
> DataSet<Tuple2<String, MyPojo>> myDS;
> myDS.writeAsFormattedText("hdfs:///myOutPath", 
>   new TextFormatter<Tuple2<String, MyPojo>>() {
>     @Override
>     public String format(Tuple2<String, MyPojo> input) {
>       return input.f0+" -> "+
>              input.f1.getWhatEver()+"  and "+
>              input.f1.getSomethingElse();
>     });
> ```
> Internally, we would use the default TextOutputFormat but with a previous Map for formatting.
> ---------------- Imported from GitHub ----------------
> Url: https://github.com/stratosphere/stratosphere/issues/834
> Created by: [fhueske|https://github.com/fhueske]
> Labels: enhancement, java api, simple-issue, user satisfaction, 
> Milestone: Release 0.6 (unplanned)
> Created at: Mon May 19 14:39:51 CEST 2014
> State: open



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