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https://issues.apache.org/jira/browse/FLINK-991?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14057343#comment-14057343
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Mariem Ayadi commented on FLINK-991:
------------------------------------
In the [Java API
documentation|http://flink.incubator.apache.org/docs/0.6-SNAPSHOT/java_api_guide.html]
(Reduce on grouped DataSet section), we still mention that in order to group a
POJO DataSet, one uses a KeySelector function.
{code:borderStyle=solid}
DataSet<WC> wordCounts = words
// DataSet grouping with inline-defined KeySelector
function
.groupBy(
new KeySelector<WC, String>() {
public String getKey(WC wc) { return wc.word; }
})
{code}
My understanding is that with [Aljoscha's
fix|https://github.com/apache/incubator-flink/commit/3f87fc9f1cc2f0e18552e6ec5e9449228a942726],
we no longer need to do so
{code:borderStyle=solid}
DataSet<WC> counts = tokenized
+ .groupBy("word")
+ .reduce(new ReduceFunction<WC>() {
+ public WC reduce(WC value1, WC value2) {
+ return new WC(value1.word,
value1.count + value2.count);
+ }
+ });
{code}
Please clarify. It'll help me modify the proper parts of the documentation
accordingly.
> Add documentation for POJO expression keys
> ------------------------------------------
>
> Key: FLINK-991
> URL: https://issues.apache.org/jira/browse/FLINK-991
> Project: Flink
> Issue Type: Bug
> Components: Documentation, Java API
> Affects Versions: 0.6-incubating
> Reporter: Fabian Hueske
> Assignee: Mariem Ayadi
> Labels: starter
>
> The Java API documentation needs to be extended to reflect the extensions
> added by FLINK-908.
> These are basically expression keys for POJO objects, i.e., selecting public
> fields of POJOs as keys by their names.
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