[SPARK-3788] [yarn] Fix compareFs to do the right thing for HDFS namespaces.

HA and viewfs use namespaces instead of host names, so you can't
resolve them since that will fail. So be smarter to avoid doing
unnecessary work.

Author: Marcelo Vanzin <vanzin@cloudera.com>

Closes #2649 from vanzin/SPARK-3788 and squashes the following commits:

fedbc73 [Marcelo Vanzin] Update comment.
c938845 [Marcelo Vanzin] Use Objects.equal() to avoid issues with ==.
9f7b571 [Marcelo Vanzin] [SPARK-3788] [yarn] Fix compareFs to do the right thing for HA, federation.
[SPARK-3848] yarn alpha doesn't build on master

yarn alpha build was broken by #2432
as it added an argument to YarnAllocator but not to yarn/alpha YarnAllocationHandler
commit https://github.com/apache/spark/commit/79e45c9323455a51f25ed9acd0edd8682b4bbb88

Author: Kousuke Saruta <sarutak@oss.nttdata.co.jp>

Closes #2715 from sarutak/SPARK-3848 and squashes the following commits:

bafb8d1 [Kousuke Saruta] Fixed parameters for the default constructor of alpha/YarnAllocatorHandler.
HOTFIX: Use correct Hadoop profile in build
[SPARK-3841] [mllib] Pretty-print params for ML examples

Provide a parent class for the Params case classes used in many MLlib examples, where the parent class pretty-prints the case class fields:
Param1Name	Param1Value
Param2Name	Param2Value
...
Using this class will make it easier to print test settings to logs.

Also, updated DecisionTreeRunner to print a little more info.

CC: mengxr

Author: Joseph K. Bradley <joseph.kurata.bradley@gmail.com>

Closes #2700 from jkbradley/dtrunner-update and squashes the following commits:

cff873f [Joseph K. Bradley] Merge remote-tracking branch 'upstream/master' into dtrunner-update
7a08ae4 [Joseph K. Bradley] code review comment updates
b4d2043 [Joseph K. Bradley] Merge remote-tracking branch 'upstream/master' into dtrunner-update
d8228a7 [Joseph K. Bradley] Merge remote-tracking branch 'upstream/master' into dtrunner-update
0fc9c64 [Joseph K. Bradley] Added abstract TestParams class for mllib example parameters
12b7798 [Joseph K. Bradley] Added abstract class TestParams for pretty-printing Params values
5f84f03 [Joseph K. Bradley] Merge remote-tracking branch 'upstream/master' into dtrunner-update
f7441b6 [Joseph K. Bradley] Merge remote-tracking branch 'upstream/master' into dtrunner-update
19eb6fc [Joseph K. Bradley] Updated DecisionTreeRunner to print training time.
[SPARK-3843][Minor] Cleanup scalastyle.txt at the end of running dev/scalastyle

dev/scalastyle create a log file 'scalastyle.txt'. it is overwrote per running but never deleted even though dev/mima and dev/lint-python delete their log files.

Author: Kousuke Saruta <sarutak@oss.nttdata.co.jp>

Closes #2702 from sarutak/scalastyle-txt-cleanup and squashes the following commits:

d6e238e [Kousuke Saruta] Fixed dev/scalastyle to cleanup scalastyle.txt
[SPARK-3831] [SQL] Filter rule Improvement and bool expression optimization.

If we write the filter which is always FALSE like

    SELECT * from person WHERE FALSE;

200 tasks will run. I think, 1 task is enough.

And current optimizer cannot optimize the case NOT is duplicated like

    SELECT * from person WHERE NOT ( NOT (age > 30));

The filter rule above should be simplified

Author: Kousuke Saruta <sarutak@oss.nttdata.co.jp>

Closes #2692 from sarutak/SPARK-3831 and squashes the following commits:

25f3e20 [Kousuke Saruta] Merge branch 'master' of git://git.apache.org/spark into SPARK-3831
23c750c [Kousuke Saruta] Improved unsupported predicate test case
a11b9f3 [Kousuke Saruta] Modified NOT predicate test case in PartitionBatchPruningSuite
8ea872b [Kousuke Saruta] Fixed the number of tasks when the data of  LocalRelation is empty.
[SPARK-3713][SQL] Uses JSON to serialize DataType objects

This PR uses JSON instead of `toString` to serialize `DataType`s. The latter is not only hard to parse but also flaky in many cases.

Since we already write schema information to Parquet metadata in the old style, we have to reserve the old `DataType` parser and ensure downward compatibility. The old parser is now renamed to `CaseClassStringParser` and moved into `object DataType`.

JoshRosen davies Please help review PySpark related changes, thanks!

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

Closes #2563 from liancheng/datatype-to-json and squashes the following commits:

fc92eb3 [Cheng Lian] Reverts debugging code, simplifies primitive type JSON representation
438c75f [Cheng Lian] Refactors PySpark DataType JSON SerDe per comments
6b6387b [Cheng Lian] Removes debugging code
6a3ee3a [Cheng Lian] Addresses per review comments
dc158b5 [Cheng Lian] Addresses PEP8 issues
99ab4ee [Cheng Lian] Adds compatibility est case for Parquet type conversion
a983a6c [Cheng Lian] Adds PySpark support
f608c6e [Cheng Lian] De/serializes DataType objects from/to JSON
[SQL][Doc] Keep Spark SQL README.md up to date

marmbrus
Update README.md to be consistent with Spark 1.1

Author: Liquan Pei <liquanpei@gmail.com>

Closes #2706 from Ishiihara/SparkSQL-readme and squashes the following commits:

33b9d4b [Liquan Pei] keep README.md up to date
[SPARK-3707] [SQL] Fix bug of type coercion in DIV

Calling `BinaryArithmetic.dataType` will throws exception until it's resolved, but in type coercion rule `Division`, seems doesn't follow this.

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

Closes #2559 from chenghao-intel/type_coercion and squashes the following commits:

199a85d [Cheng Hao] Simplify the divide rule
dc55218 [Cheng Hao] fix bug of type coercion in div
[SPARK-3810][SQL] Makes PreInsertionCasts handle partitions properly

Includes partition keys into account when applying `PreInsertionCasts` rule.

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

Closes #2672 from liancheng/fix-pre-insert-casts and squashes the following commits:

def1a1a [Cheng Lian] Makes PreInsertionCasts handle partitions properly
[SQL] Prevents per row dynamic dispatching and pattern matching when inserting Hive values

Builds all wrappers at first according to object inspector types to avoid per row costs.

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

Closes #2592 from liancheng/hive-value-wrapper and squashes the following commits:

9696559 [Cheng Lian] Passes all tests
4998666 [Cheng Lian] Prevents per row dynamic dispatching and pattern matching when inserting Hive values
[SPARK-3857] Create joins package for various join operators.

Author: Reynold Xin <rxin@apache.org>

Closes #2719 from rxin/sql-join-break and squashes the following commits:

0c0082b [Reynold Xin] Fix line length.
cbc664c [Reynold Xin] Rename join -> joins package.
a070d44 [Reynold Xin] Fix line length in HashJoin
a39be8c [Reynold Xin] [SPARK-3857] Create a join package for various join operators.
Fetch from branch v4 in Spark EC2 script.
[SPARK-3856][MLLIB] use norm operator after breeze 0.10 upgrade

Got warning msg:

~~~
[warn] /Users/meng/src/spark/mllib/src/main/scala/org/apache/spark/mllib/feature/Normalizer.scala:50: method norm in trait NumericOps is deprecated: Use norm(XXX) instead of XXX.norm
[warn]     var norm = vector.toBreeze.norm(p)
~~~

dbtsai

Author: Xiangrui Meng <meng@databricks.com>

Closes #2718 from mengxr/SPARK-3856 and squashes the following commits:

4f38169 [Xiangrui Meng] use norm operator
[SPARK-2805] Upgrade to akka 2.3.4

Upgrade to akka 2.3.4

Author: Anand Avati <avati@redhat.com>

Closes #1685 from avati/SPARK-1812-akka-2.3 and squashes the following commits:

57a2315 [Anand Avati] SPARK-1812: streaming - remove tests which depend on akka.actor.IO
2a551d3 [Anand Avati] SPARK-1812: core - upgrade to akka 2.3.4
[SPARK-3844][UI] Truncate appName in WebUI if it is too long

Truncate appName in WebUI if it is too long.

Author: Xiangrui Meng <meng@databricks.com>

Closes #2707 from mengxr/truncate-app-name and squashes the following commits:

87834ce [Xiangrui Meng] move scala import below java
c7111dc [Xiangrui Meng] truncate appName in WebUI if it is too long
add spark.driver.memory to config docs

It took me a minute to track this down, so I thought it could be useful to have it in the docs.

I'm unsure if 512mb is the default for spark.driver.memory? Also - there could be a better value for the 'description' to differentiate it from spark.executor.memory.

Author: nartz <nartzpod@gmail.com>
Author: Nathan Artz <nathanartz@Nathans-MacBook-Pro.local>

Closes #2410 from nartz/docs/add-spark-driver-memory-to-config-docs and squashes the following commits:

a2f6c62 [nartz] Update configuration.md
74521b8 [Nathan Artz] add spark.driver.memory to config docs
[SPARK-3158][MLLIB]Avoid 1 extra aggregation for DecisionTree training

Currently, the implementation does one unnecessary aggregation step. The aggregation step for level L (to choose splits) gives enough information to set the predictions of any leaf nodes at level L+1. We can use that info and skip the aggregation step for the last level of the tree (which only has leaf nodes).

### Implementation Details

Each node now has a `impurity` field and the `predict` is changed from type `Double` to type `Predict`(this can be used to compute predict probability in the future) When compute best splits for each node, we also compute impurity and predict for the child nodes, which is used to constructed newly allocated child nodes. So at level L, we have set impurity and predict for nodes at level L +1.
If level L+1 is the last level, then we can avoid aggregation. What's more, calculation of parent impurity in

Top nodes for each tree needs to be treated differently because we have to compute impurity and predict for them first. In `binsToBestSplit`, if current node is top node(level == 0), we calculate impurity and predict first.
after finding best split, top node's predict and impurity is set to the calculated value. Non-top nodes's impurity and predict are already calculated and don't need to be recalculated again. I have considered to add a initialization step to set top nodes' impurity and predict and then we can treat all nodes in the same way, but this will need a lot of duplication of code(all the code to do seq operation(BinSeqOp) needs to be duplicated), so I choose the current way.

 CC mengxr manishamde jkbradley, please help me review this, thanks.

Author: Qiping Li <liqiping1991@gmail.com>

Closes #2708 from chouqin/avoid-agg and squashes the following commits:

8e269ea [Qiping Li] adjust code and comments
eefeef1 [Qiping Li] adjust comments and check child nodes' impurity
c41b1b6 [Qiping Li] fix pyspark unit test
7ad7a71 [Qiping Li] fix unit test
822c912 [Qiping Li] add comments and unit test
e41d715 [Qiping Li] fix bug in test suite
6cc0333 [Qiping Li] SPARK-3158: Avoid 1 extra aggregation for DecisionTree training
[Minor] use norm operator after breeze 0.10 upgrade

cc mengxr

Author: GuoQiang Li <witgo@qq.com>

Closes #2730 from witgo/SPARK-3856 and squashes the following commits:

2cffce1 [GuoQiang Li] use norm operator after breeze 0.10 upgrade