[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.
[SPARK-1672][MLLIB] Separate user and product partitioning in ALS

Some clean up work following #593.

1. Allow to set different number user blocks and number product blocks in `ALS`.
2. Update `MovieLensALS` to reflect the change.

Author: Tor Myklebust <tmyklebu@gmail.com>
Author: Xiangrui Meng <meng@databricks.com>

Closes #1014 from mengxr/SPARK-1672 and squashes the following commits:

0e910dd [Xiangrui Meng] change private[this] to private[recommendation]
36420c7 [Xiangrui Meng] set exclusion rules for ALS
9128b77 [Xiangrui Meng] Merge remote-tracking branch 'apache/master' into SPARK-1672
294efe9 [Xiangrui Meng] Merge remote-tracking branch 'apache/master' into SPARK-1672
9bab77b [Xiangrui Meng] clean up add numUserBlocks and numProductBlocks to MovieLensALS
84c8e8c [Xiangrui Meng] Merge branch 'master' into SPARK-1672
d17a8bf [Xiangrui Meng] merge master
a4925fd [Tor Myklebust] Style.
bd8a75c [Tor Myklebust] Merge branch 'master' of github.com:apache/spark into alsseppar
021f54b [Tor Myklebust] Separate user and product blocks.
dcf583a [Tor Myklebust] Remove the partitioner member variable; instead, thread that needle everywhere it needs to go.
23d6f91 [Tor Myklebust] Stop making the partitioner configurable.
495784f [Tor Myklebust] Merge branch 'master' of https://github.com/apache/spark
674933a [Tor Myklebust] Fix style.
40edc23 [Tor Myklebust] Fix missing space.
f841345 [Tor Myklebust] Fix daft bug creating 'pairs', also for -> foreach.
5ec9e6c [Tor Myklebust] Clean a couple of things up using 'map'.
36a0f43 [Tor Myklebust] Make the partitioner private.
d872b09 [Tor Myklebust] Add negative id ALS test.
df27697 [Tor Myklebust] Support custom partitioners.  Currently we use the same partitioner for users and products.
c90b6d8 [Tor Myklebust] Scramble user and product ids before bucketing.
c774d7d [Tor Myklebust] Make the partitioner a member variable and use it instead of modding directly.
[SPARK-2044] Pluggable interface for shuffles

This is a first cut at moving shuffle logic behind a pluggable interface, as described at https://issues.apache.org/jira/browse/SPARK-2044, to let us more easily experiment with new shuffle implementations. It moves the existing shuffle code to a class HashShuffleManager behind a general ShuffleManager interface.

Two things are still missing to make this complete:
* MapOutputTracker needs to be hidden behind the ShuffleManager interface; this will also require adding methods to ShuffleManager that will let the DAGScheduler interact with it as it does with the MapOutputTracker today
* The code to do map-sides and reduce-side combine in ShuffledRDD, PairRDDFunctions, etc needs to be moved into the ShuffleManager's readers and writers

However, some of these may also be done later after we merge the current interface.

Author: Matei Zaharia <matei@databricks.com>

Closes #1009 from mateiz/pluggable-shuffle and squashes the following commits:

7a09862 [Matei Zaharia] review comments
be33d3f [Matei Zaharia] review comments
1513d4e [Matei Zaharia] Add ASF header
ac56831 [Matei Zaharia] Bug fix and better error message
4f681ba [Matei Zaharia] Move write part of ShuffleMapTask to ShuffleManager
f6f011d [Matei Zaharia] Move hash shuffle reader behind ShuffleManager interface
55c7717 [Matei Zaharia] Changed RDD code to use ShuffleReader
75cc044 [Matei Zaharia] Partial work to move hash shuffle in
'killFuture' is never used

Author: Yadong <qiyadong2010@gmail.com>

Closes #1052 from watermen/bug-fix1 and squashes the following commits:

409d09a [Yadong] 'killFuture' is never used
Cleanup on Connection and ConnectionManager

Simple cleanup on Connection and ConnectionManager to make IDE happy while working of issue:
1. Replace var with var
2. Add parentheses to Queue#dequeu to be consistent with side-effects.
3. Remove return on final line of a method.

Author: Henry Saputra <henry.saputra@gmail.com>

Closes #1060 from hsaputra/cleanup_connection_classes and squashes the following commits:

245fd09 [Henry Saputra] Cleanup on Connection and ConnectionManager to make IDE happy while working of issue: 1. Replace var with var 2. Add parentheses to Queue#dequeu to be consistent with side-effects. 3. Remove return on final line of a method.
fixed typo in docstring for min()

Hi, I found this typo while learning spark and thought I'd do a pull request.

Author: Jeff Thompson <jeffreykeatingthompson@gmail.com>

Closes #1065 from jkthompson/docstring-typo-minmax and squashes the following commits:

29b6a26 [Jeff Thompson] fixed typo in docstring for min()
SPARK-554.  Add aggregateByKey.

Author: Sandy Ryza <sandy@cloudera.com>

Closes #705 from sryza/sandy-spark-554 and squashes the following commits:

2302b8f [Sandy Ryza] Add MIMA exclude
f52e0ad [Sandy Ryza] Fix Python tests for real
2f3afa3 [Sandy Ryza] Fix Python test
0b735e9 [Sandy Ryza] Fix line lengths
ae56746 [Sandy Ryza] Fix doc (replace T with V)
c2be415 [Sandy Ryza] Java and Python aggregateByKey
23bf400 [Sandy Ryza] SPARK-554.  Add aggregateByKey.
[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
[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-1843: Replace assemble-deps with env variable.

(This change is actually small, I moved some logic into
compute-classpath that was previously in spark-class).

Assemble deps has existed for a while to allow developers to
run local code with new changes quickly. When I'm developing I
typically use a simpler approach which just prepends the Spark
classes to the classpath before the assembly jar. This is well
defined in the JVM and the Spark classes take precedence over those
in the assembly.

This approach is portable across both builds which is the main reason I'd
like to switch to it. It's also a bit easier to toggle on and off quickly.

The way you use this is the following:
```
$ ./bin/spark-shell # Use spark with the normal assembly
$ export SPARK_PREPEND_CLASSES=true
$ ./bin/spark-shell # Now it's using compiled classes
$ unset SPARK_PREPEND_CLASSES
$ ./bin/spark-shell # Back to normal
```

Author: Patrick Wendell <pwendell@gmail.com>

Closes #877 from pwendell/assemble-deps and squashes the following commits:

8a11345 [Patrick Wendell] Merge remote-tracking branch 'apache/master' into assemble-deps
faa3168 [Patrick Wendell] Adding a warning for compatibility
3f151a7 [Patrick Wendell] Small fix
bbfb73c [Patrick Wendell] Review feedback
328e9f8 [Patrick Wendell] SPARK-1843: Replace assemble-deps with env variable.
SPARK-2085: [MLlib] Apply user-specific regularization instead of uniform regularization in ALS

The current implementation of ALS takes a single regularization parameter and apply it on both of the user factors and the product factors. This kind of regularization can be less effective while user number is significantly larger than the number of products (and vice versa). For example, if we have 10M users and 1K product, regularization on user factors will dominate. Following the discussion in [this thread](http://apache-spark-user-list.1001560.n3.nabble.com/possible-bug-in-Spark-s-ALS-implementation-tt2567.html#a2704), the implementation in this PR will regularize each factor vector by #ratings * lambda.

Author: Shuo Xiang <sxiang@twitter.com>

Closes #1026 from coderxiang/als-reg and squashes the following commits:

93dfdb4 [Shuo Xiang] Merge remote-tracking branch 'upstream/master' into als-reg
b98f19c [Shuo Xiang] merge latest master
52c7b58 [Shuo Xiang] Apply user-specific regularization instead of uniform regularization in Alternating Least Squares (ALS)
document laziness of parallelize

Took me several hours to figure out this behavior. It would be good to highlight it in the documentation.

Author: Ariel Rabkin <asrabkin@cs.princeton.edu>

Closes #1070 from asrabkin/master and squashes the following commits:

29a076e [Ariel Rabkin] doc fix
SPARK-1939 Refactor takeSample method in RDD to use ScaSRS

Modified the takeSample method in RDD to use the ScaSRS sampling technique to improve performance. Added a private method that computes sampling rate > sample_size/total to ensure sufficient sample size with success rate >= 0.9999. Added a unit test for the private method to validate choice of sampling rate.

Author: Doris Xin <doris.s.xin@gmail.com>
Author: dorx <doris.s.xin@gmail.com>
Author: Xiangrui Meng <meng@databricks.com>

Closes #916 from dorx/takeSample and squashes the following commits:

5b061ae [Doris Xin] merge master
444e750 [Doris Xin] edge cases
3de882b [dorx] Merge pull request #2 from mengxr/SPARK-1939
82dde31 [Xiangrui Meng] update pyspark's takeSample
48d954d [Doris Xin] remove unused imports from RDDSuite
fb1452f [Doris Xin] allowing num to be greater than count in all cases
1481b01 [Doris Xin] washing test tubes and making coffee
dc699f3 [Doris Xin] give back imports removed by accident in rdd.py
64e445b [Doris Xin] logwarnning as soon as it enters the while loop
55518ed [Doris Xin] added TODO for logging in rdd.py
eff89e2 [Doris Xin] addressed reviewer comments.
ecab508 [Doris Xin] "fixed checkstyle violation
0a9b3e3 [Doris Xin] "reviewer comment addressed"
f80f270 [Doris Xin] Merge branch 'master' into takeSample
ae3ad04 [Doris Xin] fixed edge cases to prevent overflow
065ebcd [Doris Xin] Merge branch 'master' into takeSample
9bdd36e [Doris Xin] Check sample size and move computeFraction
e3fd6a6 [Doris Xin] Merge branch 'master' into takeSample
7cab53a [Doris Xin] fixed import bug in rdd.py
ffea61a [Doris Xin] SPARK-1939: Refactor takeSample method in RDD
1441977 [Doris Xin] SPARK-1939 Refactor takeSample method in RDD to use ScaSRS
[Minor] Fix style, formatting and naming in BlockManager etc.

This is a precursor to a bigger change. I wanted to separate out the relatively insignificant changes so the ultimate PR is not inflated.

(Warning: this PR is full of unimportant nitpicks)

Author: Andrew Or <andrewor14@gmail.com>

Closes #1058 from andrewor14/bm-minor and squashes the following commits:

8e12eaf [Andrew Or] SparkException -> BlockException
c36fd53 [Andrew Or] Make parts of BlockManager more readable
0a5f378 [Andrew Or] Entry -> MemoryEntry
e9762a5 [Andrew Or] Tone down string interpolation (minor reverts)
c4de9ac [Andrew Or] Merge branch 'master' of github.com:apache/spark into bm-minor
b3470f1 [Andrew Or] More string interpolation (minor)
7f9dcab [Andrew Or] Use string interpolation (minor)
94a425b [Andrew Or] Refactor against duplicate code + minor changes
8a6a7dc [Andrew Or] Exception -> SparkException
97c410f [Andrew Or] Deal with MIMA excludes
2480f1d [Andrew Or] Fixes in StorgeLevel.scala
abb0163 [Andrew Or] Style, formatting and naming fixes
[SPARK-1516]Throw exception in yarn client instead of run system.exit directly.

All the changes is in  the package of "org.apache.spark.deploy.yarn":
    1) Throw exception in ClinetArguments and ClientBase instead of exit directly.
    2) in Client's main method, if exception is caught, it will exit with code 1, otherwise exit with code 0.

After the fix, if user integrate the spark yarn client into their applications, when the argument is wrong or the running is finished, the application won't be terminated.

Author: John Zhao <jzhao@alpinenow.com>

Closes #490 from codeboyyong/jira_1516_systemexit_inyarnclient and squashes the following commits:

138cb48 [John Zhao] [SPARK-1516]Throw exception in yarn clinet instead of run system.exit directly. All the changes is in  the package of "org.apache.spark.deploy.yarn": 1) Add a ClientException with an exitCode 2) Throws exception in ClinetArguments and ClientBase instead of exit directly 3) in Client's main method, catch exception and exit with the exitCode.
[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.
[HOTFIX] add math3 version to pom

Passed `mvn package`.

Author: Xiangrui Meng <meng@databricks.com>

Closes #1075 from mengxr/takeSample-fix and squashes the following commits:

45b4590 [Xiangrui Meng] add math3 version to pom
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
Update docs and use the entire dataset to infer the schema.
Merge remote-tracking branch 'upstream/master' into newJson

Conflicts:
	sql/core/src/main/scala/org/apache/spark/sql/SQLContext.scala