[SPARK-3204][SQL] MaxOf would be foldable if both left and right are foldable.

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

Closes #2116 from ueshin/issues/SPARK-3204 and squashes the following commits:

7d9b107 [Takuya UESHIN] Make MaxOf foldable if both left and right are foldable.

(cherry picked from commit d299e2bf2f6733a6267b7ce85e2b288608b17db3)
Signed-off-by: Michael Armbrust <michael@databricks.com>
[SPARK-2929][SQL] Refactored Thrift server and CLI suites

Removed most hard coded timeout, timing assumptions and all `Thread.sleep`. Simplified IPC and synchronization with `scala.sys.process` and future/promise so that the test suites can run more robustly and faster.

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

Closes #1856 from liancheng/thriftserver-tests and squashes the following commits:

2d914ca [Cheng Lian] Minor refactoring
0e12e71 [Cheng Lian] Cleaned up test output
0ee921d [Cheng Lian] Refactored Thrift server and CLI suites

(cherry picked from commit cae9414d3805c6cf00eab6a6144d8f90cd0212f8)
Signed-off-by: Michael Armbrust <michael@databricks.com>
[SPARK-3058] [SQL] Support EXTENDED for EXPLAIN

Provide `extended` keyword support for `explain` command in SQL. e.g.
```
explain extended select key as a1, value as a2 from src where key=1;
== Parsed Logical Plan ==
Project ['key AS a1#3,'value AS a2#4]
 Filter ('key = 1)
  UnresolvedRelation None, src, None

== Analyzed Logical Plan ==
Project [key#8 AS a1#3,value#9 AS a2#4]
 Filter (CAST(key#8, DoubleType) = CAST(1, DoubleType))
  MetastoreRelation default, src, None

== Optimized Logical Plan ==
Project [key#8 AS a1#3,value#9 AS a2#4]
 Filter (CAST(key#8, DoubleType) = 1.0)
  MetastoreRelation default, src, None

== Physical Plan ==
Project [key#8 AS a1#3,value#9 AS a2#4]
 Filter (CAST(key#8, DoubleType) = 1.0)
  HiveTableScan [key#8,value#9], (MetastoreRelation default, src, None), None

Code Generation: false
== RDD ==
(2) MappedRDD[14] at map at HiveContext.scala:350
  MapPartitionsRDD[13] at mapPartitions at basicOperators.scala:42
  MapPartitionsRDD[12] at mapPartitions at basicOperators.scala:57
  MapPartitionsRDD[11] at mapPartitions at TableReader.scala:112
  MappedRDD[10] at map at TableReader.scala:240
  HadoopRDD[9] at HadoopRDD at TableReader.scala:230
```

It's the sub task of #1847. But can go without any dependency.

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

Closes #1962 from chenghao-intel/explain_extended and squashes the following commits:

295db74 [Cheng Hao] Fix bug in printing the simple execution plan
48bc989 [Cheng Hao] Support EXTENDED for EXPLAIN

(cherry picked from commit 156eb3966176de02ec3ec90ae10e50a7ebfbbf4f)
Signed-off-by: Michael Armbrust <michael@databricks.com>
[SQL] logWarning should be logInfo in getResultSetSchema

Author: wangfei <wangfei_hello@126.com>

Closes #1939 from scwf/patch-5 and squashes the following commits:

f952d10 [wangfei] [SQL] logWarning should be logInfo in getResultSetSchema

(cherry picked from commit 507a1b520063ad3e10b909767d9e3fd72d24415b)
Signed-off-by: Michael Armbrust <michael@databricks.com>
[SPARK-3011][SQL] _temporary directory should be filtered out by sqlContext.parquetFile

fix compile error on hadoop 0.23 for the pull request #1924.

Author: Chia-Yung Su <chiayung@appier.com>

Closes #1959 from joesu/bugfix-spark3011 and squashes the following commits:

be30793 [Chia-Yung Su] remove .* and _* except _metadata
8fe2398 [Chia-Yung Su] add note to explain
40ea9bd [Chia-Yung Su] fix hadoop-0.23 compile error
c7e44f2 [Chia-Yung Su] match syntax
f8fc32a [Chia-Yung Su] filter out tmp dir

(cherry picked from commit 4243bb6634aca5b9ddf6d42778aa7b4866ce6256)
Signed-off-by: Michael Armbrust <michael@databricks.com>
SPARK-2481: The environment variables SPARK_HISTORY_OPTS is covered in spark-env.sh

Author: witgo <witgo@qq.com>
Author: GuoQiang Li <witgo@qq.com>

Closes #1341 from witgo/history_env and squashes the following commits:

b4fd9f8 [GuoQiang Li] review commit
0ebe401 [witgo] *-history-server.sh load spark-config.sh

(cherry picked from commit 9f04db17e50568d5580091add9100693177d7c4f)
Signed-off-by: Andrew Or <andrewor14@gmail.com>