Author: Davies Liu <davies@databricks.com>

Closes #6311 from davies/rollup and squashes the following commits:

0261db1 [Davies Liu] use @since
a51ca6b [Davies Liu] Merge branch 'master' of github.com:apache/spark into rollup
8ad5af4 [Davies Liu] Update dataframe.py
ade3841 [Davies Liu] add DataFrame.rollup/cube in Python

Add version info for public Python SQL API.

cc rxin

Author: Davies Liu <davies@databricks.com>

Closes #6295 from davies/versions and squashes the following commits:

cfd91e6 [Davies Liu] add more version for DataFrame API
600834d [Davies Liu] add version to SQL API docs

cc rxin, please take a quick look, I'm working on tests.

Author: Davies Liu <davies@databricks.com>

Closes #6238 from davies/readwrite and squashes the following commits:

c7200eb [Davies Liu] update tests
9cbf01b [Davies Liu] Merge branch 'master' of github.com:apache/spark into readwrite
f0c5a04 [Davies Liu] use sqlContext.read.load
5f68bc8 [Davies Liu] update tests
6437e9a [Davies Liu] Merge branch 'master' of github.com:apache/spark into readwrite
bcc6668 [Davies Liu] add reader amd writer API in Python

Fixed the following warnings in `make clean html` under `python/docs`:

~~~
/Users/meng/src/spark/python/pyspark/mllib/evaluation.py:docstring of pyspark.mllib.evaluation.RankingMetrics.ndcgAt:3: ERROR: Unexpected indentation.
/Users/meng/src/spark/python/pyspark/mllib/evaluation.py:docstring of pyspark.mllib.evaluation.RankingMetrics.ndcgAt:4: WARNING: Block quote ends without a blank line; unexpected unindent.
/Users/meng/src/spark/python/pyspark/mllib/fpm.py:docstring of pyspark.mllib.fpm.FPGrowth.train:3: ERROR: Unexpected indentation.
/Users/meng/src/spark/python/pyspark/mllib/fpm.py:docstring of pyspark.mllib.fpm.FPGrowth.train:4: WARNING: Block quote ends without a blank line; unexpected unindent.
/Users/meng/src/spark/python/pyspark/sql/__init__.py:docstring of pyspark.sql.DataFrame.replace:16: WARNING: Field list ends without a blank line; unexpected unindent.
/Users/meng/src/spark/python/pyspark/streaming/kafka.py:docstring of pyspark.streaming.kafka.KafkaUtils.createRDD:8: ERROR: Unexpected indentation.
/Users/meng/src/spark/python/pyspark/streaming/kafka.py:docstring of pyspark.streaming.kafka.KafkaUtils.createRDD:9: WARNING: Block quote ends without a blank line; unexpected unindent.
~~~

davies

Author: Xiangrui Meng <meng@databricks.com>

Closes #6221 from mengxr/SPARK-6657 and squashes the following commits:

e3f83fe [Xiangrui Meng] fix sql and streaming doc warnings
2b4371e [Xiangrui Meng] fix mllib python doc warnings

dataframe.py is splited into column.py, group.py and dataframe.py:
```
   360 column.py
  1223 dataframe.py
   183 group.py
```

Author: Davies Liu <davies@databricks.com>

Closes #6201 from davies/split_df and squashes the following commits:

fc8f5ab [Davies Liu] split dataframe.py into multiple files

Add an `explode` function for dataframes and modify the analyzer so that single table generating functions can be present in a select clause along with other expressions.   There are currently the following restrictions:
 - only top level TGFs are allowed (i.e. no `select(explode('list) + 1)`)
 - only one may be present in a single select to avoid potentially confusing implicit Cartesian products.

TODO:
 - [ ] Python

Author: Michael Armbrust <michael@databricks.com>

Closes #6107 from marmbrus/explodeFunction and squashes the following commits:

7ee2c87 [Michael Armbrust] whitespace
6f80ba3 [Michael Armbrust] Update dataframe.py
c176c89 [Michael Armbrust] Merge remote-tracking branch 'origin/master' into explodeFunction
81b5da3 [Michael Armbrust] style
d3faa05 [Michael Armbrust] fix self join case
f9e1e3e [Michael Armbrust] fix python, add since
4f0d0a9 [Michael Armbrust] Merge remote-tracking branch 'origin/master' into explodeFunction
e710fe4 [Michael Armbrust] add java and python
52ca0dc [Michael Armbrust] [SPARK-7548][SQL] Add explode function for dataframes.

This builds on https://github.com/apache/spark/pull/5932 and should close https://github.com/apache/spark/pull/5932 as well.

As an example:
```python
df.select(when(df['age'] == 2, 3).otherwise(4).alias("age")).collect()
```

Author: Reynold Xin <rxin@databricks.com>
Author: kaka1992 <kaka_1992@163.com>

Closes #6072 from rxin/when-expr and squashes the following commits:

8f49201 [Reynold Xin] Throw exception if otherwise is applied twice.
0455eda [Reynold Xin] Reset run-tests.
bfb9d9f [Reynold Xin] Updated documentation and test cases.
762f6a5 [Reynold Xin] Merge pull request #5932 from kaka1992/IFCASE
95724c6 [kaka1992] Update
8218d0a [kaka1992] Update
801009e [kaka1992] Update
76d6346 [kaka1992] [SPARK-7321][SQL] Add Column expression for conditional statements (if, case)

Author: Daoyuan Wang <daoyuan.wang@intel.com>

Closes #6003 from adrian-wang/pynareplace and squashes the following commits:

672efba [Daoyuan Wang] remove py2.7 feature
4a148f7 [Daoyuan Wang] to_replace support dict, value support single value, and add full tests
9e232e7 [Daoyuan Wang] rename scala map
af0268a [Daoyuan Wang] remove na
63ac579 [Daoyuan Wang] add na.replace in pyspark

Author: Reynold Xin <rxin@databricks.com>

Closes #6068 from rxin/drop-column and squashes the following commits:

9d7d5ec [Reynold Xin] [SPARK-7509][SQL] DataFrame.drop in Python for dropping columns.

This should also close https://github.com/apache/spark/pull/5870

Author: Reynold Xin <rxin@databricks.com>

Closes #6066 from rxin/dropDups and squashes the following commits:

130692f [Reynold Xin] [SPARK-7324][SQL] DataFrame.dropDuplicates

Updated Java, Scala, Python, and R.

Author: Reynold Xin <rxin@databricks.com>
Author: Shivaram Venkataraman <shivaram@cs.berkeley.edu>

Closes #5996 from rxin/groupby-retain and squashes the following commits:

aac7119 [Reynold Xin] Merge branch 'groupby-retain' of github.com:rxin/spark into groupby-retain
f6858f6 [Reynold Xin] Merge branch 'master' into groupby-retain
5f923c0 [Reynold Xin] Merge pull request #15 from shivaram/sparkr-groupby-retrain
c1de670 [Shivaram Venkataraman] Revert workaround in SparkR to retain grouped cols Based on reverting code added in commit https://github.com/amplab-extras/spark/commit/9a6be746efc9fafad88122fa2267862ef87aa0e1
b8b87e1 [Reynold Xin] Fixed DataFrameJoinSuite.
d910141 [Reynold Xin] Updated rest of the files
1e6e666 [Reynold Xin] [SPARK-7462] By default retain group by columns in aggregate

It's the first step: generalize UnresolvedGetField to support all map, struct, and array
TODO: add `apply` in Scala and `__getitem__` in Python, and unify the `getItem` and `getField` methods to one single API(or should we keep them for compatibility?).

Author: Wenchen Fan <cloud0fan@outlook.com>

Closes #5744 from cloud-fan/generalize and squashes the following commits:

715c589 [Wenchen Fan] address comments
7ea5b31 [Wenchen Fan] fix python test
4f0833a [Wenchen Fan] add python test
f515d69 [Wenchen Fan] add apply method and test cases
8df6199 [Wenchen Fan] fix python test
239730c [Wenchen Fan] fix test compile
2a70526 [Wenchen Fan] use _bin_op in dataframe.py
6bf72bc [Wenchen Fan] address comments
3f880c3 [Wenchen Fan] add java doc
ab35ab5 [Wenchen Fan] fix python test
b5961a9 [Wenchen Fan] fix style
c9d85f5 [Wenchen Fan] generalize UnresolvedGetField to support all map, struct, and array

Author: Shiti <ssaxena.ece@gmail.com>

Closes #5867 from Shiti/spark-7295 and squashes the following commits:

71a9913 [Shiti] implementation for bitwise and,or, not and xor on Column with tests and docs

Author: 云峤 <chensong.cs@alibaba-inc.com>
Author: kaka1992 <kaka_1992@163.com>

Closes #5839 from kaka1992/master and squashes the following commits:

b15360d [kaka1992] Fix python unit test in sql/test. =_= I forget to commit this file last time.
f928816 [kaka1992] Fix python style in sql/test.
d2e7f72 [kaka1992] Fix python style in sql/test.
c54d904 [kaka1992] Fix empty map bug.
7e64d1e [云峤] Update
7b9b858 [云峤] undo
f080f8d [云峤] update pep8
76f0c51 [云峤] Merge remote-tracking branch 'remotes/upstream/master'
7d62368 [云峤] [SPARK-7294] ADD BETWEEN
baf839b [云峤] [SPARK-7294] ADD BETWEEN
d11d5b9 [云峤] [SPARK-7294] ADD BETWEEN

Reduced take size from 1e8 to 1e6.

cc rxin

Author: Burak Yavuz <brkyvz@gmail.com>

Closes #5900 from brkyvz/df-cont-followup and squashes the following commits:

c11e762 [Burak Yavuz] fix grammar
b30ace2 [Burak Yavuz] address comments
a417ba5 [Burak Yavuz] [SPARK-7243][SQL] Reduce  size for Contingency Tables in DataFrames

Computes a pair-wise frequency table of the given columns. Also known as cross-tabulation.
cc mengxr rxin

Author: Burak Yavuz <brkyvz@gmail.com>

Closes #5842 from brkyvz/df-cont and squashes the following commits:

a07c01e [Burak Yavuz] addressed comments v4.1
ae9e01d [Burak Yavuz] fix test
9106585 [Burak Yavuz] addressed comments v4.0
bced829 [Burak Yavuz] fix merge conflicts
a63ad00 [Burak Yavuz] addressed comments v3.0
a0cad97 [Burak Yavuz] addressed comments v3.0
6805df8 [Burak Yavuz] addressed comments and fixed test
939b7c4 [Burak Yavuz] lint python
7f098bc [Burak Yavuz] add crosstab pyTest
fd53b00 [Burak Yavuz] added python support for crosstab
27a5a81 [Burak Yavuz] implemented crosstab

Author: 云峤 <chensong.cs@alibaba-inc.com>

Closes #5865 from kaka1992/df.show and squashes the following commits:

c79204b [云峤] Update
a1338f6 [云峤] Update python dataFrame show test and add empty df unit test.
734369c [云峤] Update python dataFrame show test and add empty df unit test.
84aec3e [云峤] Update python dataFrame show test and add empty df unit test.
159b3d5 [云峤] update
03ef434 [云峤] update
7394fd5 [云峤] update test show
ced487a [云峤] update pep8
b6e690b [云峤] Merge remote-tracking branch 'upstream/master' into df.show
30ac311 [云峤] [SPARK-7294] ADD BETWEEN
7d62368 [云峤] [SPARK-7294] ADD BETWEEN
baf839b [云峤] [SPARK-7294] ADD BETWEEN
d11d5b9 [云峤] [SPARK-7294] ADD BETWEEN

submitting this PR from a phone, excuse the brevity.
adds Pearson correlation to Dataframes, reusing the covariance calculation code

cc mengxr rxin

Author: Burak Yavuz <brkyvz@gmail.com>

Closes #5858 from brkyvz/df-corr and squashes the following commits:

285b838 [Burak Yavuz] addressed comments v2.0
d10babb [Burak Yavuz] addressed comments v0.2
4b74b24 [Burak Yavuz] Merge branch 'master' of github.com:apache/spark into df-corr
4fe693b [Burak Yavuz] addressed comments v0.1
a682d06 [Burak Yavuz] ready for PR

Author: Dean Chen <deanchen5@gmail.com>

Closes #5866 from deanchen/patch-1 and squashes the following commits:

0028bc4 [Dean Chen] Fix typo in Dataframes.py introduced in [SPARK-3444]

The python api for DataFrame's plus addressed your comments from previous PR.
rxin

Author: Burak Yavuz <brkyvz@gmail.com>

Closes #5859 from brkyvz/df-freq-py2 and squashes the following commits:

f9aa9ce [Burak Yavuz] addressed comments v0.1
4b25056 [Burak Yavuz] added python api for freqItems

Add support for changing the log level at run time through the SparkContext. Based on an earlier PR, #2433 includes CR feedback from pwendel & davies

Author: Holden Karau <holden@pigscanfly.ca>

Closes #5791 from holdenk/SPARK-3444-provide-an-easy-way-to-change-log-level-r2 and squashes the following commits:

3bf3be9 [Holden Karau] fix exception
42ba873 [Holden Karau] fix exception
9117244 [Holden Karau] Only allow valid log levels, throw exception if invalid log level.
338d7bf [Holden Karau] rename setLoggingLevel to setLogLevel
fac14a0 [Holden Karau] Fix style errors
d9d03f3 [Holden Karau] Add support for changing the log level at run time through the SparkContext. Based on an earlier PR, #2433 includes CR feedback from @pwendel & @davies

Added the calculation of covariance between two columns to DataFrames.

cc mengxr rxin

Author: Burak Yavuz <brkyvz@gmail.com>

Closes #5825 from brkyvz/df-cov and squashes the following commits:

cb18046 [Burak Yavuz] changed to sample covariance
f2e862b [Burak Yavuz] fixed failed test
51e39b8 [Burak Yavuz] moved implementation
0c6a759 [Burak Yavuz] addressed math comments
8456eca [Burak Yavuz] fix pyStyle3
aa2ad29 [Burak Yavuz] fix pyStyle2
4e97a50 [Burak Yavuz] Merge branch 'master' of github.com:apache/spark into df-cov
e3b0b85 [Burak Yavuz] addressed comments v0.1
a7115f1 [Burak Yavuz] fix python style
7dc6dbc [Burak Yavuz] reorder imports
408cb77 [Burak Yavuz] initial commit

small fixes regarding comments in PR #5761

cc rxin

Author: Burak Yavuz <brkyvz@gmail.com>

Closes #5795 from brkyvz/split-followup and squashes the following commits:

369c522 [Burak Yavuz] changed wording a little
1ea456f [Burak Yavuz] Addressed follow up comments

This is built on top of kaka1992 's PR #5711 using Logical plans.

Author: Burak Yavuz <brkyvz@gmail.com>

Closes #5761 from brkyvz/random-sample and squashes the following commits:

a1fb0aa [Burak Yavuz] remove unrelated file
69669c3 [Burak Yavuz] fix broken test
1ddb3da [Burak Yavuz] copy base
6000328 [Burak Yavuz] added python api and fixed test
3c11d1b [Burak Yavuz] fixed broken test
f400ade [Burak Yavuz] fix build errors
2384266 [Burak Yavuz] addressed comments v0.1
e98ebac [Burak Yavuz] [SPARK-7156][SQL] support RandomSplit in DataFrames

I believe column access via `__getattr__` is bad and shouldn't be implicitly encouraged by the error message when accessing a non-existing attribute on DataFrame. This patch changes the error message from 'no such column'  to the more generic 'no such attribute', which is also what Pandas DFs will throw.

Author: ksonj <kson@siberie.de>

Closes #5771 from ksonj/master and squashes the following commits:

bcc2220 [ksonj] Better error message on access to non-existing attribute

This patch adds SQL to the set of excluded libraries when
generating a callSite. This makes the callSite mechanism work
properly for the data frame API. I also added a small improvement for
JDBC queries where we just use the string "Spark JDBC Server Query"
instead of trying to give a callsite that doesn't make any sense
to the user.

Before (DF):
![screen shot 2015-04-28 at 1 29 26 pm](https://cloud.githubusercontent.com/assets/320616/7380170/ef63bfb0-edae-11e4-989c-f88a5ba6bbee.png)

After (DF):
![screen shot 2015-04-28 at 1 34 58 pm](https://cloud.githubusercontent.com/assets/320616/7380181/fa7f6d90-edae-11e4-9559-26f163ed63b8.png)

After (JDBC):
![screen shot 2015-04-28 at 2 00 10 pm](https://cloud.githubusercontent.com/assets/320616/7380185/02f5b2a4-edaf-11e4-8e5b-99bdc3df66dd.png)

Author: Patrick Wendell <patrick@databricks.com>

Closes #5757 from pwendell/dataframes and squashes the following commits:

0d931a4 [Patrick Wendell] Attempting to fix PySpark tests
85bf740 [Patrick Wendell] [SPARK-7204] Fix callsite for dataframe operations.

This pr tries to provide a way to let python users workaround https://issues.apache.org/jira/browse/SPARK-6231.

Author: Yin Huai <yhuai@databricks.com>

Closes #5634 from yhuai/pythonDFAlias and squashes the following commits:

8465acd [Yin Huai] Add an alias to a Python DF.

Author: Reynold Xin <rxin@databricks.com>

Closes #5638 from rxin/joinUsing and squashes the following commits:

13e9cc9 [Reynold Xin] Code review + Python.
b1bd914 [Reynold Xin] [SPARK-7059][SQL] Create a DataFrame join API to facilitate equijoin and self join.

This PR enable auto_convert in JavaGateway, then we could register a converter for a given types, for example, date and datetime.

There are two bugs related to auto_convert, see [1] and [2], we workaround it in this PR.

[1]  https://github.com/bartdag/py4j/issues/160
[2] https://github.com/bartdag/py4j/issues/161

cc rxin JoshRosen

Author: Davies Liu <davies@databricks.com>

Closes #5570 from davies/py4j_date and squashes the following commits:

eb4fa53 [Davies Liu] fix tests in python 3
d17d634 [Davies Liu] rollback changes in mllib
2e7566d [Davies Liu] convert tuple into ArrayList
ceb3779 [Davies Liu] Update rdd.py
3c373f3 [Davies Liu] support date and datetime by auto_convert
cb094ff [Davies Liu] enable auto convert

Author: Elisey Zanko <elisey.zanko@gmail.com>

Closes #5361 from 31z4/spark-6661 and squashes the following commits:

73c5d79 [Elisey Zanko] Python type errors should print type, not object

As a follow up PR to #5544.

cc davies

Author: Reynold Xin <rxin@databricks.com>

Closes #5558 from rxin/sort-doc-improvement and squashes the following commits:

f4c276f [Reynold Xin] Review feedback.
d2dcf24 [Reynold Xin] Minor fix to SPARK-6958: Improve Python docstring for DataFrame.sort.

```
select(['cola', 'colb'])

groupby(['colA', 'colB'])
groupby([df.colA, df.colB])

df.sort('A', ascending=True)
df.sort(['A', 'B'], ascending=True)
df.sort(['A', 'B'], ascending=[1, 0])
```

cc rxin

Author: Davies Liu <davies@databricks.com>

Closes #5544 from davies/compatibility and squashes the following commits:

4944058 [Davies Liu] add docstrings
adb2816 [Davies Liu] Merge branch 'master' of github.com:apache/spark into compatibility
bcbbcab [Davies Liu] support ascending as list
8dabdf0 [Davies Liu] improve API compatibility to pandas

Support access columns by index in Python:
```
>>> df[df[0] > 3].collect()
[Row(age=5, name=u'Bob')]
```

Access items in ArrayType or MapType
```
>>> df.select(df.l.getItem(0), df.d.getItem("key")).show()
>>> df.select(df.l[0], df.d["key"]).show()
```

Access field in StructType
```
>>> df.select(df.r.getField("b")).show()
>>> df.select(df.r.a).show()
```

Author: Davies Liu <davies@databricks.com>

Closes #5513 from davies/access and squashes the following commits:

e04d5a0 [Davies Liu] Update run-tests-jenkins
7ada9eb [Davies Liu] update timeout
d125ac4 [Davies Liu] check column name, improve scala tests
6b62540 [Davies Liu] fix test
db15b42 [Davies Liu] Merge branch 'master' of github.com:apache/spark into access
6c32e79 [Davies Liu] add scala tests
11f1df3 [Davies Liu] improve accessor for nested types

This PR update PySpark to support Python 3 (tested with 3.4).

Known issue: unpickle array from Pyrolite is broken in Python 3, those tests are skipped.

TODO: ec2/spark-ec2.py is not fully tested with python3.

Author: Davies Liu <davies@databricks.com>
Author: twneale <twneale@gmail.com>
Author: Josh Rosen <joshrosen@databricks.com>

Closes #5173 from davies/python3 and squashes the following commits:

d7d6323 [Davies Liu] fix tests
6c52a98 [Davies Liu] fix mllib test
99e334f [Davies Liu] update timeout
b716610 [Davies Liu] Merge branch 'master' of github.com:apache/spark into python3
cafd5ec [Davies Liu] adddress comments from @mengxr
bf225d7 [Davies Liu] Merge branch 'master' of github.com:apache/spark into python3
179fc8d [Davies Liu] tuning flaky tests
8c8b957 [Davies Liu] fix ResourceWarning in Python 3
5c57c95 [Davies Liu] Merge branch 'master' of github.com:apache/spark into python3
4006829 [Davies Liu] fix test
2fc0066 [Davies Liu] add python3 path
71535e9 [Davies Liu] fix xrange and divide
5a55ab4 [Davies Liu] Merge branch 'master' of github.com:apache/spark into python3
125f12c [Davies Liu] Merge branch 'master' of github.com:apache/spark into python3
ed498c8 [Davies Liu] fix compatibility with python 3
820e649 [Davies Liu] Merge branch 'master' of github.com:apache/spark into python3
e8ce8c9 [Davies Liu] Merge branch 'master' of github.com:apache/spark into python3
ad7c374 [Davies Liu] fix mllib test and warning
ef1fc2f [Davies Liu] fix tests
4eee14a [Davies Liu] Merge branch 'master' of github.com:apache/spark into python3
20112ff [Davies Liu] Merge branch 'master' of github.com:apache/spark into python3
59bb492 [Davies Liu] fix tests
1da268c [Davies Liu] Merge branch 'master' of github.com:apache/spark into python3
ca0fdd3 [Davies Liu] fix code style
9563a15 [Davies Liu] add imap back for python 2
0b1ec04 [Davies Liu] make python examples work with Python 3
d2fd566 [Davies Liu] Merge branch 'master' of github.com:apache/spark into python3
a716d34 [Davies Liu] test with python 3.4
f1700e8 [Davies Liu] fix test in python3
671b1db [Davies Liu] fix test in python3
692ff47 [Davies Liu] fix flaky test
7b9699f [Davies Liu] invalidate import cache for Python 3.3+
9c58497 [Davies Liu] fix kill worker
309bfbf [Davies Liu] keep compatibility
5707476 [Davies Liu] cleanup, fix hash of string in 3.3+
8662d5b [Davies Liu] Merge branch 'master' of github.com:apache/spark into python3
f53e1f0 [Davies Liu] fix tests
70b6b73 [Davies Liu] compile ec2/spark_ec2.py in python 3
a39167e [Davies Liu] support customize class in __main__
814c77b [Davies Liu] run unittests with python 3
7f4476e [Davies Liu] mllib tests passed
d737924 [Davies Liu] pass ml tests
375ea17 [Davies Liu] SQL tests pass
6cc42a9 [Davies Liu] rename
431a8de [Davies Liu] streaming tests pass
78901a7 [Davies Liu] fix hash of serializer in Python 3
24b2f2e [Davies Liu] pass all RDD tests
35f48fe [Davies Liu] run future again
1eebac2 [Davies Liu] fix conflict in ec2/spark_ec2.py
6e3c21d [Davies Liu] make cloudpickle work with Python3
2fb2db3 [Josh Rosen] Guard more changes behind sys.version; still doesn't run
1aa5e8f [twneale] Turned out `pickle.DictionaryType is dict` == True, so swapped it out
7354371 [twneale] buffer --> memoryview  I'm not super sure if this a valid change, but the 2.7 docs recommend using memoryview over buffer where possible, so hoping it'll work.
b69ccdf [twneale] Uses the pure python pickle._Pickler instead of c-extension _pickle.Pickler. It appears pyspark 2.7 uses the pure python pickler as well, so this shouldn't degrade pickling performance (?).
f40d925 [twneale] xrange --> range
e104215 [twneale] Replaces 2.7 types.InstsanceType with 3.4 `object`....could be horribly wrong depending on how types.InstanceType is used elsewhere in the package--see http://bugs.python.org/issue8206
79de9d0 [twneale] Replaces python2.7 `file` with 3.4 _io.TextIOWrapper
2adb42d [Josh Rosen] Fix up some import differences between Python 2 and 3
854be27 [Josh Rosen] Run `futurize` on Python code:
7c5b4ce [Josh Rosen] Remove Python 3 check in shell.py.

This PR change the internal representation for StringType from java.lang.String to UTF8String, which is implemented use ArrayByte.

This PR should not break any public API, Row.getString() will still return java.lang.String.

This is the first step of improve the performance of String in SQL.

cc rxin

Author: Davies Liu <davies@databricks.com>

Closes #5350 from davies/string and squashes the following commits:

3b7bfa8 [Davies Liu] fix schema of AddJar
2772f0d [Davies Liu] fix new test failure
6d776a9 [Davies Liu] Merge branch 'master' of github.com:apache/spark into string
59025c8 [Davies Liu] address comments from @marmbrus
341ec2c [Davies Liu] turn off scala style check in UTF8StringSuite
744788f [Davies Liu] Merge branch 'master' of github.com:apache/spark into string
b04a19c [Davies Liu] add comment for getString/setString
08d897b [Davies Liu] Merge branch 'master' of github.com:apache/spark into string
5116b43 [Davies Liu] rollback unrelated changes
1314a37 [Davies Liu] address comments from Yin
867bf50 [Davies Liu] fix String filter push down
13d9d42 [Davies Liu] Merge branch 'master' of github.com:apache/spark into string
2089d24 [Davies Liu] add hashcode check back
ac18ae6 [Davies Liu] address comment
fd11364 [Davies Liu] optimize UTF8String
8d17f21 [Davies Liu] fix hive compatibility tests
e5fa5b8 [Davies Liu] remove clone in UTF8String
28f3d81 [Davies Liu] Merge branch 'master' of github.com:apache/spark into string
28d6f32 [Davies Liu] refactor
537631c [Davies Liu] some comment about Date
9f4c194 [Davies Liu] convert data type for data source
956b0a4 [Davies Liu] fix hive tests
73e4363 [Davies Liu] Merge branch 'master' of github.com:apache/spark into string
9dc32d1 [Davies Liu] fix some hive tests
23a766c [Davies Liu] refactor
8b45864 [Davies Liu] fix codegen with UTF8String
bb52e44 [Davies Liu] fix scala style
c7dd4d2 [Davies Liu] fix some catalyst tests
38c303e [Davies Liu] fix python sql tests
5f9e120 [Davies Liu] fix sql tests
6b499ac [Davies Liu] fix style
a85fb27 [Davies Liu] refactor
d32abd1 [Davies Liu] fix utf8 for python api
4699c3a [Davies Liu] use Array[Byte] in UTF8String
21f67c6 [Davies Liu] cleanup
685fd07 [Davies Liu] use UTF8String instead of String for StringType

Use `sqlContext` in PySpark shell, make it consistent with SQL programming guide. `sqlCtx` is also kept for compatibility.

Author: Davies Liu <davies@databricks.com>

Closes #5425 from davies/sqlCtx and squashes the following commits:

af67340 [Davies Liu] sqlCtx -> sqlContext
15a278f [Davies Liu] use sqlContext in python shell

Author: Reynold Xin <rxin@databricks.com>

Closes #5287 from rxin/pyspark-df-doc-cleanup-context and squashes the following commits:

1841b60 [Reynold Xin] Lint.
f2007f1 [Reynold Xin] functions and types.
bc3b72b [Reynold Xin] More improvements to DataFrame Python doc.
ac1d4c0 [Reynold Xin] Bug fix.
b163365 [Reynold Xin] Python fix. Added Experimental flag to DataFrameNaFunctions.
608422d [Reynold Xin] [Doc] Cleanup context.py Python docs.

To maintain consistency with the Scala API.

Author: Reynold Xin <rxin@databricks.com>

Closes #5284 from rxin/df-na-alias and squashes the following commits:

19f46b7 [Reynold Xin] Show DataFrameNaFunctions in docs.
6618118 [Reynold Xin] [SPARK-6623][SQL] Alias DataFrame.na.drop and DataFrame.na.fill in Python.

This pull request adds variants of DataFrame.na.drop and DataFrame.na.fill to the Scala/Java API, and DataFrame.fillna and DataFrame.dropna to the Python API.

Author: Reynold Xin <rxin@databricks.com>

Closes #5274 from rxin/df-missing-value and squashes the following commits:

4ee1b98 [Reynold Xin] Improve error reporting in Python.
33a330c [Reynold Xin] Remove replace for now.
bc4fdbb [Reynold Xin] Added documentation for replace.
d56f5a5 [Reynold Xin] Added replace for Scala/Java.
2385d00 [Reynold Xin] Feedback from Xiangrui on "how".
914a374 [Reynold Xin] fill with map.
185c67e [Reynold Xin] Allow specifying column subsets in fill.
749eb47 [Reynold Xin] fillna
249b94e [Reynold Xin] Removing undefined functions.
6a73c68 [Reynold Xin] Missing file.
67d7003 [Reynold Xin] [SPARK-6119][SQL] DataFrame.na.drop (Scala/Java) and DataFrame.dropna (Python)

Author: Reynold Xin <rxin@databricks.com>

Closes #5238 from rxin/pyspark-docs and squashes the following commits:

c285951 [Reynold Xin] Reset deprecation warning.
8c1031e [Reynold Xin] inferSchema
dd91b1a [Reynold Xin] [DOC] Improvements to Python docs.