[SPARK-19287][CORE][STREAMING] JavaPairRDD flatMapValues requires function returning Iterable, not Iterator

[srowen]

What changes were proposed in this pull request?

Fix old oversight in API: Java flatMapValues needs a FlatMapFunction

How was this patch tested?

Existing tests.

[SparkQA]

Test build #97217 has finished for PR 22690 at commit b1a88d5.

• This patch fails to build.
• This patch merges cleanly.
• This patch adds no public classes.

[SparkQA]

Test build #97223 has finished for PR 22690 at commit 587aa89.

• This patch fails to build.
• This patch merges cleanly.
• This patch adds no public classes.

[SparkQA]

Test build #97225 has finished for PR 22690 at commit 6c6c1a3.

• This patch fails MiMa tests.
• This patch merges cleanly.
• This patch adds no public classes.

[SparkQA]

Test build #97226 has finished for PR 22690 at commit a35b54f.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[felixcheung]

breaking API change?

[srowen]

Yes, for 3.0. it's an old API mistake

[SparkQA]

Test build #97316 has finished for PR 22690 at commit 216bf7c.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[srowen]

Merged to master

[HyukjinKwon]

cc @cloud-fan and @gatorsmile

Should we update migration guide as well?

[srowen]

Yeah let me go back and add a note about several recent changes like this.

[srowen]

Actually sorry for the ignorant question @HyukjinKwon but is there a migration guide for things outside SQL and MLlib? those are the two I've found. This one isn't specific to those two. I tagged the JIRA as release-notes because this deserves a mention to be sure. By itself there's not much more to know about the migration than that a function return type changed.