Add comment about defaultMinPartitions

[idanz]

Added a comment about using math.min for choosing default partition count

[AmplabJenkins]

Can one of the admins verify this patch?

[srowen]

(Can you make the description descriptive? it becomes a commit message.)

[JoshRosen]

Jenkins, this is ok to test.

[SparkQA]

Test build #25906 has started for PR 4102 at commit 50e9d58.

• This patch merges cleanly.

[SparkQA]

Test build #25906 has finished for PR 4102 at commit 50e9d58.

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

[AmplabJenkins]

Test FAILed.
Refer to this link for build results (access rights to CI server needed):
https://amplab.cs.berkeley.edu/jenkins//job/SparkPullRequestBuilder/25906/
Test FAILed.

[JoshRosen]

This is a spurious test failure: it looks like a test using EasyMock failed during test suite initialization, which leaked a SparkContext and triggered this error.

[JoshRosen]

Jenkins, retest this please.

[SparkQA]

Test build #25914 has started for PR 4102 at commit 50e9d58.

• This patch merges cleanly.

[SparkQA]

Test build #25914 has finished for PR 4102 at commit 50e9d58.

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

[AmplabJenkins]

Test FAILed.
Refer to this link for build results (access rights to CI server needed):
https://amplab.cs.berkeley.edu/jenkins//job/SparkPullRequestBuilder/25914/
Test FAILed.

[JoshRosen]

Jenkins, retest this please.

[SparkQA]

Test build #25921 has started for PR 4102 at commit 50e9d58.

• This patch merges cleanly.

[SparkQA]

Test build #25921 has finished for PR 4102 at commit 50e9d58.

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

[AmplabJenkins]

Test PASSed.
Refer to this link for build results (access rights to CI server needed):
https://amplab.cs.berkeley.edu/jenkins//job/SparkPullRequestBuilder/25921/
Test PASSed.

[JoshRosen]

I'm going to merge this into master (1.3.0) and leave a note on the JIRA to say that this has been addressed in the documentation. Thanks!