[SPARK-12953][Examples]RDDRelation writer set overwrite mode

[shijinkui]

https://issues.apache.org/jira/browse/SPARK-12953

fix error when run RDDRelation.main():
"path file:/Users/sjk/pair.parquet already exists"

Set DataFrameWriter's mode to SaveMode.Overwrite

[rxin]

Thanks for submitting a patch. However, I don't think these examples are here for you to keep running them -- it is just an example.

[rxin]

Can you close this pull request? Thanks.

[shijinkui]

@rxin This case throw exception at the second time of running. Unit test is import to project, example is useful for spark user. :)
this problem is not important and critical, if can be fixed by the way, maybe better for user :)

[rxin]

That's fair -- if you reopen I can merge it provided that tests pass.

[SparkQA]

Test build #2452 has finished for PR 10864 at commit 958a419.

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

[shijinkui]

hi, @rxin, I have reopened, please trigger the test

[SparkQA]

Test build #2456 has finished for PR 10864 at commit 2de63ec.

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

[shijinkui]

test it

[JoshRosen]

Jenkins, retest this please.

[SparkQA]

Test build #50154 has finished for PR 10864 at commit 04c4ef4.

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

[shijinkui]

@JoshRosen fix checkstyle failure, please retest it.

[JoshRosen]

Jenkins, retest this please

[SparkQA]

Test build #51054 has finished for PR 10864 at commit d768182.

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

[JoshRosen]

LGTM, so I'm merging this to master. Thanks!