[SPARK-1704][SQL] Fully support EXPLAIN commands as SchemaRDD.

This PR attempts to resolve [SPARK-1704](https://issues.apache.org/jira/browse/SPARK-1704) by introducing a physical plan for EXPLAIN commands, which just prints out the debug string (containing various SparkSQL's plans) of the corresponding QueryExecution for the actual query.

Author: Zongheng Yang <zongheng.y@gmail.com>

Closes #1003 from concretevitamin/explain-cmd and squashes the following commits:

5b7911f [Zongheng Yang] Add a regression test.
1bfa379 [Zongheng Yang] Modify output().
719ada9 [Zongheng Yang] Override otherCopyArgs for ExplainCommandPhysical.
4318fd7 [Zongheng Yang] Make all output one Row.
439c6ab [Zongheng Yang] Minor cleanups.
408f574 [Zongheng Yang] SPARK-1704: Add CommandStrategy and ExplainCommandPhysical.

(cherry picked from commit a9ec033c8cf489898cc47e2043bd9e86b7df1ff8)
Signed-off-by: Michael Armbrust <michael@databricks.com>
[SPARK-1508][SQL] Add SQLConf to SQLContext.

This PR (1) introduces a new class SQLConf that stores key-value properties for a SQLContext (2) clean up the semantics of various forms of SET commands.

The SQLConf class unlocks user-controllable optimization opportunities; for example, user can now override the number of partitions used during an Exchange. A SQLConf can be accessed and modified programmatically through its getters and setters. It can also be modified through SET commands executed by `sql()` or `hql()`. Note that users now have the ability to change a particular property for different queries inside the same Spark job, unlike settings configured in SparkConf.

For SET commands: "SET" will return all properties currently set in a SQLConf, "SET key" will return the key-value pair (if set) or an undefined message, and "SET key=value" will call the setter on SQLConf, and if a HiveContext is used, it will be executed in Hive as well.

Author: Zongheng Yang <zongheng.y@gmail.com>

Closes #956 from concretevitamin/sqlconf and squashes the following commits:

4968c11 [Zongheng Yang] Very minor cleanup.
d74dde5 [Zongheng Yang] Remove the redundant mkQueryExecution() method.
c129b86 [Zongheng Yang] Merge remote-tracking branch 'upstream/master' into sqlconf
26c40eb [Zongheng Yang] Make SQLConf a trait and have SQLContext mix it in.
dd19666 [Zongheng Yang] Update a comment.
baa5d29 [Zongheng Yang] Remove default param for shuffle partitions accessor.
5f7e6d8 [Zongheng Yang] Add default num partitions.
22d9ed7 [Zongheng Yang] Fix output() of Set physical. Add SQLConf param accessor method.
e9856c4 [Zongheng Yang] Use java.util.Collections.synchronizedMap on a Java HashMap.
88dd0c8 [Zongheng Yang] Remove redundant SET Keyword.
271f0b1 [Zongheng Yang] Minor change.
f8983d1 [Zongheng Yang] Minor changes per review comments.
1ce8a5e [Zongheng Yang] Invoke runSqlHive() in SQLConf#get for the HiveContext case.
b766af9 [Zongheng Yang] Remove a test.
d52e1bd [Zongheng Yang] De-hardcode number of shuffle partitions for BasicOperators (read from SQLConf).
555599c [Zongheng Yang] Bullet-proof (relatively) parsing SET per review comment.
c2067e8 [Zongheng Yang] Mark SQLContext transient and put it in a second param list.
2ea8cdc [Zongheng Yang] Wrap long line.
41d7f09 [Zongheng Yang] Fix imports.
13279e6 [Zongheng Yang] Refactor the logic of eagerly processing SET commands.
b14b83e [Zongheng Yang] In a HiveContext, make SQLConf a subset of HiveConf.
6983180 [Zongheng Yang] Move a SET test to SQLQuerySuite and make it complete.
5b67985 [Zongheng Yang] New line at EOF.
c651797 [Zongheng Yang] Add commands.scala.
efd82db [Zongheng Yang] Clean up semantics of several cases of SET.
c1017c2 [Zongheng Yang] WIP in changing SetCommand to take two Options (for different semantics of SETs).
0f00d86 [Zongheng Yang] Add a test for singleton set command in SQL.
41acd75 [Zongheng Yang] Add a test for hql() in HiveQuerySuite.
2276929 [Zongheng Yang] Fix default hive result for set commands in HiveComparisonTest.
3b0c71b [Zongheng Yang] Remove Parser for set commands. A few other fixes.
d0c4578 [Zongheng Yang] Tmux typo.
0ecea46 [Zongheng Yang] Changes for HiveQl and HiveContext.
ce22d80 [Zongheng Yang] Fix parsing issues.
cb722c1 [Zongheng Yang] Finish up SQLConf patch.
4ebf362 [Zongheng Yang] First cut at SQLConf inside SQLContext.

(cherry picked from commit 08ed9ad81397b71206c4dc903bfb94b6105691ed)
Signed-off-by: Michael Armbrust <michael@databricks.com>
Moved hiveOperators.scala to the right package folder

The package is `org.apache.spark.sql.hive.execution`, while the file was placed under `sql/hive/src/main/scala/org/apache/spark/sql/hive/`.

Author: Cheng Lian <lian.cs.zju@gmail.com>

Closes #1029 from liancheng/moveHiveOperators and squashes the following commits:

d632eb8 [Cheng Lian] Moved hiveOperators.scala to the right package folder

(cherry picked from commit a9a461c594fd20e46947e318095df60bddb67559)
Signed-off-by: Michael Armbrust <michael@databricks.com>
[SPARK-1978] In some cases, spark-yarn does not automatically restart the failed container

Author: witgo <witgo@qq.com>

Closes #921 from witgo/allocateExecutors and squashes the following commits:

bc3aa66 [witgo] review commit
8800eba [witgo] Merge branch 'master' of https://github.com/apache/spark into allocateExecutors
32ac7af [witgo] review commit
056b8c7 [witgo] Merge branch 'master' of https://github.com/apache/spark into allocateExecutors
04c6f7e [witgo] Merge branch 'master' into allocateExecutors
aff827c [witgo] review commit
5c376e0 [witgo] Merge branch 'master' of https://github.com/apache/spark into allocateExecutors
1faf4f4 [witgo] Merge branch 'master' into allocateExecutors
3c464bd [witgo] add time limit to allocateExecutors
e00b656 [witgo] In some cases, yarn does not automatically restart the container
HOTFIX: Fix Python tests on Jenkins.

Author: Patrick Wendell <pwendell@gmail.com>

Closes #1036 from pwendell/jenkins-test and squashes the following commits:

9c99856 [Patrick Wendell] Better output during tests
71e7b74 [Patrick Wendell] Removing incorrect python path
74984db [Patrick Wendell] HOTFIX: Allow PySpark tests to run on Jenkins.
(cherry picked from commit fb499be1ac935b6f91046ec8ff23ac1267c82342)

Signed-off-by: Patrick Wendell <pwendell@gmail.com>
HOTFIX: Increase time limit for Bagel test

The test was timing out on some slow EC2 workers.

Author: Ankur Dave <ankurdave@gmail.com>

Closes #1037 from ankurdave/bagel-test-time-limit and squashes the following commits:

67fd487 [Ankur Dave] Increase time limit for Bagel test
(cherry picked from commit 55a0e87ee4655106d5e0ed799b11e77f68a17dbb)

Signed-off-by: Patrick Wendell <pwendell@gmail.com>
[SPARK-2076][SQL] Pushdown the join filter & predication for outer join

As the rule described in https://cwiki.apache.org/confluence/display/Hive/OuterJoinBehavior, we can optimize the SQL Join by pushing down the Join predicate and Where predicate.

Author: Cheng Hao <hao.cheng@intel.com>

Closes #1015 from chenghao-intel/join_predicate_push_down and squashes the following commits:

10feff9 [Cheng Hao] fix bug of changing the join type in PredicatePushDownThroughJoin
44c6700 [Cheng Hao] Add logical to support pushdown the join filter
0bce426 [Cheng Hao] Pushdown the join filter & predicate for outer join

(cherry picked from commit db0c038a66cb228bcb62a5607cd0ed013d0f9f20)
Signed-off-by: Michael Armbrust <michael@databricks.com>
[SQL] Add average overflow test case from #978

By @egraldlo.

Author: egraldlo <egraldlo@gmail.com>
Author: Michael Armbrust <michael@databricks.com>

Closes #1033 from marmbrus/pr/978 and squashes the following commits:

e228c5e [Michael Armbrust] Remove "test".
762aeaf [Michael Armbrust] Remove unneeded rule. More descriptive name for test table.
d414cd7 [egraldlo] fommatting issues
1153f75 [egraldlo] do best to avoid overflowing in function avg().

(cherry picked from commit 1abbde0e89131ad95e793ac1834c392db46b448e)
Signed-off-by: Michael Armbrust <michael@databricks.com>
[SPARK-1998] SparkFlumeEvent with body bigger than 1020 bytes are not re...

flume event sent to Spark will fail if the body is too large and numHeaders is greater than zero

Author: joyyoj <sunshch@gmail.com>

Closes #951 from joyyoj/master and squashes the following commits:

f4660c5 [joyyoj] [SPARK-1998] SparkFlumeEvent with body bigger than 1020 bytes are not read properly
(cherry picked from commit 29660443077619ee854025b8d0d3d64181724054)

Signed-off-by: Patrick Wendell <pwendell@gmail.com>
HOTFIX: clear() configs in SQLConf-related unit tests.

Thanks goes to @liancheng, who pointed out that `sql/test-only *.SQLConfSuite *.SQLQuerySuite` passed but `sql/test-only *.SQLQuerySuite *.SQLConfSuite` failed. The reason is that some tests use the same test keys and without clear()'ing, they get carried over to other tests. This hotfix simply adds some `clear()` calls.

This problem was not evident on Jenkins before probably because `parallelExecution` is not set to `false` for `sqlCoreSettings`.

Author: Zongheng Yang <zongheng.y@gmail.com>

Closes #1040 from concretevitamin/sqlconf-tests and squashes the following commits:

6d14ceb [Zongheng Yang] HOTFIX: clear() confs in SQLConf related unit tests.

(cherry picked from commit 601032f5bfe2dcdc240bfcc553f401e6facbf5ec)
Signed-off-by: Michael Armbrust <michael@databricks.com>
[SPARK-2093] [SQL] NullPropagation should use exact type value.

`NullPropagation` should use exact type value when transform `Count` or `Sum`.

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

Closes #1034 from ueshin/issues/SPARK-2093 and squashes the following commits:

65b6ff1 [Takuya UESHIN] Modify the literal value of the result of transformation from Sum to long value.
830c20b [Takuya UESHIN] Add Cast to the result of transformation from Count.
9314806 [Takuya UESHIN] Fix NullPropagation to use exact type value.

(cherry picked from commit 0402bd77ec786d1fa6cfd7f9cc3aa97c7ab16fd8)
Signed-off-by: Michael Armbrust <michael@databricks.com>
[SPARK-1968][SQL] SQL/HiveQL command for caching/uncaching tables

JIRA issue: [SPARK-1968](https://issues.apache.org/jira/browse/SPARK-1968)

This PR added support for SQL/HiveQL command for caching/uncaching tables:

```
scala> sql("CACHE TABLE src")
...
res0: org.apache.spark.sql.SchemaRDD =
SchemaRDD[0] at RDD at SchemaRDD.scala:98
== Query Plan ==
CacheCommandPhysical src, true

scala> table("src")
...
res1: org.apache.spark.sql.SchemaRDD =
SchemaRDD[3] at RDD at SchemaRDD.scala:98
== Query Plan ==
InMemoryColumnarTableScan [key#0,value#1], (HiveTableScan [key#0,value#1], (MetastoreRelation default, src, None), None), false

scala> isCached("src")
res2: Boolean = true

scala> sql("CACHE TABLE src")
...
res3: org.apache.spark.sql.SchemaRDD =
SchemaRDD[4] at RDD at SchemaRDD.scala:98
== Query Plan ==
CacheCommandPhysical src, false

scala> table("src")
...
res4: org.apache.spark.sql.SchemaRDD =
SchemaRDD[11] at RDD at SchemaRDD.scala:98
== Query Plan ==
HiveTableScan [key#2,value#3], (MetastoreRelation default, src, None), None

scala> isCached("src")
res5: Boolean = false
```

Things also work for `hql`.

Author: Cheng Lian <lian.cs.zju@gmail.com>

Closes #1038 from liancheng/sqlCacheTable and squashes the following commits:

ecb7194 [Cheng Lian] Trimmed the SQL string before parsing special commands
6f4ce42 [Cheng Lian] Moved logical command classes to a separate file
3458a24 [Cheng Lian] Added comment for public API
f0ffacc [Cheng Lian] Added isCached() predicate
15ec6d2 [Cheng Lian] Added "(UN)CACHE TABLE" SQL/HiveQL statements

(cherry picked from commit 0266a0c8a70e0fbaeb0df63031f7a750ffc31a80)
Signed-off-by: Michael Armbrust <michael@databricks.com>
SPARK-2107: FilterPushdownSuite doesn't need Junit jar.

Author: Qiuzhuang.Lian <Qiuzhuang.Lian@gmail.com>

Closes #1046 from Qiuzhuang/master and squashes the following commits:

0a9921a [Qiuzhuang.Lian] SPARK-2107: FilterPushdownSuite doesn't need Junit jar.
[SPARK-2108] Mark SparkContext methods that return block information as developer API's

Author: Prashant Sharma <prashant.s@imaginea.com>

Closes #1047 from ScrapCodes/SPARK-2108/mark-as-dev-api and squashes the following commits:

073ee34 [Prashant Sharma] [SPARK-2108] Mark SparkContext methods that return block information as developer API's
(cherry picked from commit e508f599f88baaa31a3498fb0bdbafdbc303119e)

Signed-off-by: Patrick Wendell <pwendell@gmail.com>
SPARK-2113: awaitTermination() after stop() will hang in Spark Stremaing

Author: Lars Albertsson <lalle@spotify.com>

Closes #1001 from lallea/contextwaiter_stopped and squashes the following commits:

93cd314 [Lars Albertsson] Mend StreamingContext stop() followed by awaitTermination().
(cherry picked from commit 4d5c12aa1c54c49377a4bafe3bcc4993d5e1a552)

Signed-off-by: Patrick Wendell <pwendell@gmail.com>
[SPARK-2042] Prevent unnecessary shuffle triggered by take()

This PR implements `take()` on a `SchemaRDD` by inserting a logical limit that is followed by a `collect()`. This is also accompanied by adding a catalyst optimizer rule for collapsing adjacent limits. Doing so prevents an unnecessary shuffle that is sometimes triggered by `take()`.

Author: Sameer Agarwal <sameer@databricks.com>

Closes #1048 from sameeragarwal/master and squashes the following commits:

3eeb848 [Sameer Agarwal] Fixing Tests
1b76ff1 [Sameer Agarwal] Deprecating limit(limitExpr: Expression) in v1.1.0
b723ac4 [Sameer Agarwal] Added limit folding tests
a0ff7c4 [Sameer Agarwal] Adding catalyst rule to fold two consecutive limits
8d42d03 [Sameer Agarwal] Implement trigger() as limit() followed by collect()

(cherry picked from commit 4107cce58c41160a0dc20339621eacdf8a8b1191)
Signed-off-by: Michael Armbrust <michael@databricks.com>
[SQL] Code Cleanup: Left Semi Hash Join

Some improvement for PR #837, add another case to white list and use `filter` to build result iterator.

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

Closes #1049 from adrian-wang/clean-LeftSemiJoinHash and squashes the following commits:

b314d5a [Daoyuan] change hashSet name
27579a9 [Daoyuan] add semijoin to white list and use filter to create new iterator in LeftSemiJoinBNL

Signed-off-by: Michael Armbrust <michael@databricks.com>
(cherry picked from commit ce6deb1e5b4cd40c97730fcf5dc89cb2f624bce2)
Signed-off-by: Michael Armbrust <michael@databricks.com>
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>