HOTFIX: PySpark tests should be order insensitive.

This has been messing up the SQL PySpark tests on Jenkins.

Author: Patrick Wendell <pwendell@gmail.com>

Closes #1054 from pwendell/pyspark and squashes the following commits:

1eb5487 [Patrick Wendell] False change
06f062d [Patrick Wendell] HOTFIX: PySpark tests should be order insensitive
[SPARK-2052] [SQL] Add optimization for CaseConversionExpression's.

Add optimization for `CaseConversionExpression`'s.

Author: Takuya UESHIN <ueshin@happy-camper.st>

Closes #990 from ueshin/issues/SPARK-2052 and squashes the following commits:

2568666 [Takuya UESHIN] Move some rules back.
dde7ede [Takuya UESHIN] Add tests to check if ConstantFolding can handle null literals and remove the unneeded rules from NullPropagation.
c4eea67 [Takuya UESHIN] Fix toString methods.
23e2363 [Takuya UESHIN] Make CaseConversionExpressions foldable if the child is foldable.
0ff7568 [Takuya UESHIN] Add tests for collapsing case statements.
3977d80 [Takuya UESHIN] Add optimization for CaseConversionExpression's.

(cherry picked from commit 9a2448daf984d5bb550dfe0d9e28cbb80ef5cb51)
Signed-off-by: Michael Armbrust <michael@databricks.com>
[SPARK-2088] fix NPE in toString

After deserialization, the transient field creationSiteInfo does not get backfilled with the default value, but the toString method, which is invoked by the serializer, expects the field to always be non-null. An NPE is thrown when toString is called by the serializer when creationSiteInfo is null.

Author: Doris Xin <doris.s.xin@gmail.com>

Closes #1028 from dorx/toStringNPE and squashes the following commits:

f20021e [Doris Xin] unit test for toString after desrialization
6f0a586 [Doris Xin] Merge branch 'master' into toStringNPE
f47fecf [Doris Xin] Merge branch 'master' into toStringNPE
76199c6 [Doris Xin] [SPARK-2088] fix NPE in toString

(cherry picked from commit 83c226d454722d5dea186d48070fb98652d0dafb)
Signed-off-by: Xiangrui Meng <meng@databricks.com>
[SPARK-2080] Yarn: report HS URL in client mode, correct user in cluster mode.

Yarn client mode was not setting the app's tracking URL to the
History Server's URL when configured by the user. Now client mode
behaves the same as cluster mode.

In SparkContext.scala, the "user.name" system property had precedence
over the SPARK_USER environment variable. This means that SPARK_USER
was never used, since "user.name" is always set by the JVM. In Yarn
cluster mode, this means the application always reported itself as
being run by user "yarn" (or whatever user was running the Yarn NM).
One could argue that the correct fix would be to use UGI.getCurrentUser()
here, but at least for Yarn that will match what SPARK_USER is set
to.

Author: Marcelo Vanzin <vanzin@cloudera.com>

This patch had conflicts when merged, resolved by
Committer: Thomas Graves <tgraves@apache.org>

Closes #1002 from vanzin/yarn-client-url and squashes the following commits:

4046e04 [Marcelo Vanzin] Set HS link in yarn-alpha also.
4c692d9 [Marcelo Vanzin] Yarn: report HS URL in client mode, correct user in cluster mode.
[SPARK-2135][SQL] Use planner for in-memory scans

Author: Michael Armbrust <michael@databricks.com>

Closes #1072 from marmbrus/cachedStars and squashes the following commits:

8757c8e [Michael Armbrust] Use planner for in-memory scans.

(cherry picked from commit 13f8cfdc04589b986554310965e83fe658085683)
Signed-off-by: Michael Armbrust <michael@databricks.com>
Workaround in Spark for ConcurrentModification issue (JIRA Hadoop-10456, Spark-1097)

This fix has gone into Hadoop 2.4.1. For developers using <  2.4.1, it would be good to have a workaround in Spark as well.

Fix has been tested for performance as well, no regressions found.

Author: nravi <nravi@c1704.halxg.cloudera.com>

Closes #1000 from nishkamravi2/master and squashes the following commits:

eb663ca [nravi] Merge branch 'master' of https://github.com/apache/spark
df2aeb1 [nravi] Improved fix for ConcurrentModificationIssue (Spark-1097, Hadoop-10456)
6b840f0 [nravi] Undo the fix for SPARK-1758 (the problem is fixed)
5108700 [nravi] Fix in Spark for the Concurrent thread modification issue (SPARK-1097, HADOOP-10456)
681b36f [nravi] Fix for SPARK-1758: failing test org.apache.spark.JavaAPISuite.wholeTextFiles

(cherry picked from commit 70c8116c0aecba293234edc44a7f8e58e5008649)
Signed-off-by: Reynold Xin <rxin@apache.org>
Merge branch 'branch-1.0' of github.com:apache/spark into csd-1.0