### What changes were proposed in this pull request?
Empty partition column values are not valid for partition specification. Before this PR, we accept users to do it; however, Hive metastore does not detect and disallow it too. Thus, users hit the following strange error.

```Scala
val df = spark.createDataFrame(Seq((0, "a"), (1, "b"))).toDF("partCol1", "name")
df.write.mode("overwrite").partitionBy("partCol1").saveAsTable("partitionedTable")
spark.sql("alter table partitionedTable drop partition(partCol1='')")
spark.table("partitionedTable").show()
```

In the above example, the WHOLE table is DROPPED when users specify a partition spec containing only one partition column with empty values.

When the partition columns contains more than one, Hive metastore APIs simply ignore the columns with empty values and treat it as partial spec. This is also not expected. This does not follow the actual Hive behaviors. This PR is to disallow users to specify such an invalid partition spec in the `SessionCatalog` APIs.

### How was this patch tested?
Added test cases

Author: gatorsmile <gatorsmile@gmail.com>

Closes #16583 from gatorsmile/disallowEmptyPartColValue.

## What changes were proposed in this pull request?

`dropDuplicates` will create an Alias using the same exprId, so `StreamExecution` should also replace Alias if necessary.

## How was this patch tested?

test("SPARK-19065: dropDuplicates should not create expressions using the same id")

Author: Shixiong Zhu <shixiong@databricks.com>

Closes #16564 from zsxwing/SPARK-19065.

[SPARK-19019] [PYTHON] Fix hijacked `collections.namedtuple` and port cloudpickle changes for PySpark to work with Python 3.6.0

## What changes were proposed in this pull request?

Currently, PySpark does not work with Python 3.6.0.

Running `./bin/pyspark` simply throws the error as below and PySpark does not work at all:

```
Traceback (most recent call last):
  File ".../spark/python/pyspark/shell.py", line 30, in <module>
    import pyspark
  File ".../spark/python/pyspark/__init__.py", line 46, in <module>
    from pyspark.context import SparkContext
  File ".../spark/python/pyspark/context.py", line 36, in <module>
    from pyspark.java_gateway import launch_gateway
  File ".../spark/python/pyspark/java_gateway.py", line 31, in <module>
    from py4j.java_gateway import java_import, JavaGateway, GatewayClient
  File "<frozen importlib._bootstrap>", line 961, in _find_and_load
  File "<frozen importlib._bootstrap>", line 950, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 646, in _load_unlocked
  File "<frozen importlib._bootstrap>", line 616, in _load_backward_compatible
  File ".../spark/python/lib/py4j-0.10.4-src.zip/py4j/java_gateway.py", line 18, in <module>
  File "/usr/local/Cellar/python3/3.6.0/Frameworks/Python.framework/Versions/3.6/lib/python3.6/pydoc.py", line 62, in <module>
    import pkgutil
  File "/usr/local/Cellar/python3/3.6.0/Frameworks/Python.framework/Versions/3.6/lib/python3.6/pkgutil.py", line 22, in <module>
    ModuleInfo = namedtuple('ModuleInfo', 'module_finder name ispkg')
  File ".../spark/python/pyspark/serializers.py", line 394, in namedtuple
    cls = _old_namedtuple(*args, **kwargs)
TypeError: namedtuple() missing 3 required keyword-only arguments: 'verbose', 'rename', and 'module'
```

The root cause seems because some arguments of `namedtuple` are now completely keyword-only arguments from Python 3.6.0 (See https://bugs.python.org/issue25628).

We currently copy this function via `types.FunctionType` which does not set the default values of keyword-only arguments (meaning `namedtuple.__kwdefaults__`) and this seems causing internally missing values in the function (non-bound arguments).

This PR proposes to work around this by manually setting it via `kwargs` as `types.FunctionType` seems not supporting to set this.

Also, this PR ports the changes in cloudpickle for compatibility for Python 3.6.0.

## How was this patch tested?

Manually tested with Python 2.7.6 and Python 3.6.0.

```
./bin/pyspsark
```

, manual creation of `namedtuple` both in local and rdd with Python 3.6.0,

and Jenkins tests for other Python versions.

Also,

```
./run-tests --python-executables=python3.6
```

```
Will test against the following Python executables: ['python3.6']
Will test the following Python modules: ['pyspark-core', 'pyspark-ml', 'pyspark-mllib', 'pyspark-sql', 'pyspark-streaming']
Finished test(python3.6): pyspark.sql.tests (192s)
Finished test(python3.6): pyspark.accumulators (3s)
Finished test(python3.6): pyspark.mllib.tests (198s)
Finished test(python3.6): pyspark.broadcast (3s)
Finished test(python3.6): pyspark.conf (2s)
Finished test(python3.6): pyspark.context (14s)
Finished test(python3.6): pyspark.ml.classification (21s)
Finished test(python3.6): pyspark.ml.evaluation (11s)
Finished test(python3.6): pyspark.ml.clustering (20s)
Finished test(python3.6): pyspark.ml.linalg.__init__ (0s)
Finished test(python3.6): pyspark.streaming.tests (240s)
Finished test(python3.6): pyspark.tests (240s)
Finished test(python3.6): pyspark.ml.recommendation (19s)
Finished test(python3.6): pyspark.ml.feature (36s)
Finished test(python3.6): pyspark.ml.regression (37s)
Finished test(python3.6): pyspark.ml.tuning (28s)
Finished test(python3.6): pyspark.mllib.classification (26s)
Finished test(python3.6): pyspark.mllib.evaluation (18s)
Finished test(python3.6): pyspark.mllib.clustering (44s)
Finished test(python3.6): pyspark.mllib.linalg.__init__ (0s)
Finished test(python3.6): pyspark.mllib.feature (26s)
Finished test(python3.6): pyspark.mllib.fpm (23s)
Finished test(python3.6): pyspark.mllib.random (8s)
Finished test(python3.6): pyspark.ml.tests (92s)
Finished test(python3.6): pyspark.mllib.stat.KernelDensity (0s)
Finished test(python3.6): pyspark.mllib.linalg.distributed (25s)
Finished test(python3.6): pyspark.mllib.stat._statistics (15s)
Finished test(python3.6): pyspark.mllib.recommendation (24s)
Finished test(python3.6): pyspark.mllib.regression (26s)
Finished test(python3.6): pyspark.profiler (9s)
Finished test(python3.6): pyspark.mllib.tree (16s)
Finished test(python3.6): pyspark.shuffle (1s)
Finished test(python3.6): pyspark.mllib.util (18s)
Finished test(python3.6): pyspark.serializers (11s)
Finished test(python3.6): pyspark.rdd (20s)
Finished test(python3.6): pyspark.sql.conf (8s)
Finished test(python3.6): pyspark.sql.catalog (17s)
Finished test(python3.6): pyspark.sql.column (18s)
Finished test(python3.6): pyspark.sql.context (18s)
Finished test(python3.6): pyspark.sql.group (27s)
Finished test(python3.6): pyspark.sql.dataframe (33s)
Finished test(python3.6): pyspark.sql.functions (35s)
Finished test(python3.6): pyspark.sql.types (6s)
Finished test(python3.6): pyspark.sql.streaming (13s)
Finished test(python3.6): pyspark.streaming.util (0s)
Finished test(python3.6): pyspark.sql.session (16s)
Finished test(python3.6): pyspark.sql.window (4s)
Finished test(python3.6): pyspark.sql.readwriter (35s)
Tests passed in 433 seconds
```

Author: hyukjinkwon <gurwls223@gmail.com>

Closes #16429 from HyukjinKwon/SPARK-19019.

## What changes were proposed in this pull request?

`spark.yarn.access.namenodes` configuration cannot actually reflects the usage of it, inside the code it is the Hadoop filesystems we get tokens, not NNs. So here propose to update the name of this configuration, also change the related code and doc.

## How was this patch tested?

Local verification.

Author: jerryshao <sshao@hortonworks.com>

Closes #16560 from jerryshao/SPARK-19179.

## What changes were proposed in this pull request?

This PR proposes to fix ambiguous link warnings by simply making them as code blocks for both javadoc and scaladoc.

```
[warn] .../spark/core/src/main/scala/org/apache/spark/Accumulator.scala:20: The link target "SparkContext#accumulator" is ambiguous. Several members fit the target:
[warn] .../spark/mllib/src/main/scala/org/apache/spark/mllib/optimization/GradientDescent.scala:281: The link target "runMiniBatchSGD" is ambiguous. Several members fit the target:
[warn] .../spark/mllib/src/main/scala/org/apache/spark/mllib/fpm/AssociationRules.scala:83: The link target "run" is ambiguous. Several members fit the target:
...
```

This PR also fixes javadoc8 break as below:

```
[error] .../spark/sql/core/target/java/org/apache/spark/sql/LowPrioritySQLImplicits.java:7: error: reference not found
[error]  * newProductEncoder - to disambiguate for {link List}s which are both {link Seq} and {link Product}
[error]                                                   ^
[error] .../spark/sql/core/target/java/org/apache/spark/sql/LowPrioritySQLImplicits.java:7: error: reference not found
[error]  * newProductEncoder - to disambiguate for {link List}s which are both {link Seq} and {link Product}
[error]                                                                                ^
[error] .../spark/sql/core/target/java/org/apache/spark/sql/LowPrioritySQLImplicits.java:7: error: reference not found
[error]  * newProductEncoder - to disambiguate for {link List}s which are both {link Seq} and {link Product}
[error]                                                                                                ^
[info] 3 errors
```

## How was this patch tested?

Manually via `sbt unidoc > output.txt` and the checked it via `cat output.txt | grep ambiguous`

and `sbt unidoc | grep error`.

Author: hyukjinkwon <gurwls223@gmail.com>

Closes #16604 from HyukjinKwon/SPARK-3249.

## What changes were proposed in this pull request?

Changing the default parquet logging levels to reflect the changes made in PR [#15538](https://github.com/apache/spark/pull/15538), in order to prevent the flood of log messages by default.

## How was this patch tested?

Default log output when reading from parquet 1.6 files was compared with and without this change. The change eliminates the extraneous logging and makes the output readable.

Author: Nick Lavers <nick.lavers@videoamp.com>

Closes #16580 from nicklavers/spark-19219-set_default_parquet_log_level.

## What changes were proposed in this pull request?

SET LOCATION can also work on managed table(or table created without custom path), the behavior is a little weird, but as we have already supported it, we should add a test to explicitly show the behavior.

## How was this patch tested?

N/A

Author: Wenchen Fan <wenchen@databricks.com>

Closes #16597 from cloud-fan/set-location.

## What changes were proposed in this pull request?
#16092 moves YARN resource manager related code to resource-managers/yarn directory. The test case ```YarnSchedulerBackendSuite``` was added after that but with the wrong place. I move it to correct directory in this PR.

## How was this patch tested?
Existing test.

Author: Yanbo Liang <ybliang8@gmail.com>

Closes #16595 from yanboliang/yarn.

## What changes were proposed in this pull request?

In https://github.com/apache/spark/pull/16296 , we reached a consensus that we should hide the external/managed table concept to users and only expose custom table path.

This PR renames `Catalog.createExternalTable` to `createTable`(still keep the old versions for backward compatibility), and only set the table type to EXTERNAL if `path` is specified in options.

## How was this patch tested?

new tests in `CatalogSuite`

Author: Wenchen Fan <wenchen@databricks.com>

Closes #16528 from cloud-fan/create-table.

## What changes were proposed in this pull request?

the current implementation of Spark streaming considers a batch is completed no matter the results of the jobs (https://github.com/apache/spark/blob/1169db44bc1d51e68feb6ba2552520b2d660c2c0/streaming/src/main/scala/org/apache/spark/streaming/scheduler/JobScheduler.scala#L203)
Let's consider the following case:
A micro batch contains 2 jobs and they read from two different kafka topics respectively. One of these jobs is failed due to some problem in the user defined logic, after the other one is finished successfully.
1. The main thread in the Spark streaming application will execute the line mentioned above,
2. and another thread (checkpoint writer) will make a checkpoint file immediately after this line is executed.
3. Then due to the current error handling mechanism in Spark Streaming, StreamingContext will be closed (https://github.com/apache/spark/blob/1169db44bc1d51e68feb6ba2552520b2d660c2c0/streaming/src/main/scala/org/apache/spark/streaming/scheduler/JobScheduler.scala#L214)
the user recovers from the checkpoint file, and because the JobSet containing the failed job has been removed (taken as completed) before the checkpoint is constructed, the data being processed by the failed job would never be reprocessed

This PR fix it by removing jobset from JobScheduler.jobSets only when all jobs in a jobset are successfully finished

## How was this patch tested?

existing tests

Author: CodingCat <zhunansjtu@gmail.com>
Author: Nan Zhu <zhunansjtu@gmail.com>

Closes #16542 from CodingCat/SPARK-18905.

## What changes were proposed in this pull request?

Refactored script to remove duplications and clearer purpose for each script

## How was this patch tested?

manually

Author: Felix Cheung <felixcheung_m@hotmail.com>

Closes #16249 from felixcheung/rscripts.

## What changes were proposed in this pull request?

Windows seems to be the only place with appauthor in the path, for which we should say "Apache" (and case sensitive)
Current path of `AppData\Local\spark\spark\Cache` is a bit odd.

## How was this patch tested?

manual.

Author: Felix Cheung <felixcheung_m@hotmail.com>

Closes #16590 from felixcheung/rcachedir.

## What changes were proposed in this pull request?

spark.lda passes the optimizer "em" or "online" as a string to the backend. However, LDAWrapper doesn't set optimizer based on the value from R. Therefore, for optimizer "em", the `isDistributed` field is FALSE, which should be TRUE based on scala code.

In addition, the `summary` method should bring back the results related to `DistributedLDAModel`.

## How was this patch tested?
Manual tests by comparing with scala example.
Modified the current unit test: fix the incorrect unit test and add necessary tests for `summary` method.

Author: wm624@hotmail.com <wm624@hotmail.com>

Closes #16464 from wangmiao1981/new.

## What changes were proposed in this pull request?

This PR is a follow-up to address the comments https://github.com/apache/spark/pull/16233/files#r95669988 and https://github.com/apache/spark/pull/16233/files#r95662299.

We try to wrap the child by:
1. Generate the `queryOutput` by:
    1.1. If the query column names are defined, map the column names to attributes in the child output by name;
    1.2. Else set the child output attributes to `queryOutput`.
2. Map the `queryQutput` to view output by index, if the corresponding attributes don't match, try to up cast and alias the attribute in `queryOutput` to the attribute in the view output.
3. Add a Project over the child, with the new output generated by the previous steps.
If the view output doesn't have the same number of columns neither with the child output, nor with the query column names, throw an AnalysisException.

## How was this patch tested?

Add new test cases in `SQLViewSuite`.

Author: jiangxingbo <jiangxb1987@gmail.com>

Closes #16561 from jiangxb1987/alias-view.

## What changes were proposed in this pull request?

We have a config `spark.sql.files.ignoreCorruptFiles` which can be used to ignore corrupt files when reading files in SQL. Currently the `ignoreCorruptFiles` config has two issues and can't work for Parquet:

1. We only ignore corrupt files in `FileScanRDD` . Actually, we begin to read those files as early as inferring data schema from the files. For corrupt files, we can't read the schema and fail the program. A related issue reported at http://apache-spark-developers-list.1001551.n3.nabble.com/Skip-Corrupted-Parquet-blocks-footer-tc20418.html
2. In `FileScanRDD`, we assume that we only begin to read the files when starting to consume the iterator. However, it is possibly the files are read before that. In this case, `ignoreCorruptFiles` config doesn't work too.

This patch targets Parquet datasource. If this direction is ok, we can address the same issue for other datasources like Orc.

Two main changes in this patch:

1. Replace `ParquetFileReader.readAllFootersInParallel` by implementing the logic to read footers in multi-threaded manner

    We can't ignore corrupt files if we use `ParquetFileReader.readAllFootersInParallel`. So this patch implements the logic to do the similar thing in `readParquetFootersInParallel`.

2. In `FileScanRDD`, we need to ignore corrupt file too when we call `readFunction` to return iterator.

One thing to notice is:

We read schema from Parquet file's footer. The method to read footer `ParquetFileReader.readFooter` throws `RuntimeException`, instead of `IOException`, if it can't successfully read the footer. Please check out https://github.com/apache/parquet-mr/blob/df9d8e415436292ae33e1ca0b8da256640de9710/parquet-hadoop/src/main/java/org/apache/parquet/hadoop/ParquetFileReader.java#L470. So this patch catches `RuntimeException`.  One concern is that it might also shadow other runtime exceptions other than reading corrupt files.

## How was this patch tested?

Jenkins tests.

Please review http://spark.apache.org/contributing.html before opening a pull request.

Author: Liang-Chi Hsieh <viirya@gmail.com>

Closes #16474 from viirya/fix-ignorecorrupted-parquet-files.

### What changes were proposed in this pull request?
```Scala
        sql("CREATE TABLE tab (a STRING) STORED AS PARQUET")

        // This table fetch is to fill the cache with zero leaf files
        spark.table("tab").show()

        sql(
          s"""
             |LOAD DATA LOCAL INPATH '$newPartitionDir' OVERWRITE
             |INTO TABLE tab
           """.stripMargin)

        spark.table("tab").show()
```

In the above example, the returned result is empty after table loading. The metadata cache could be out of dated after loading new data into the table, because loading/inserting does not update the cache. So far, the metadata cache is only used for data source tables. Thus, for Hive serde tables, only `parquet` and `orc` formats are facing such issues, because the Hive serde tables in the format of  parquet/orc could be converted to data source tables when `spark.sql.hive.convertMetastoreParquet`/`spark.sql.hive.convertMetastoreOrc` is on.

This PR is to refresh the metadata cache after processing the `LOAD DATA` command.

In addition, Spark SQL does not convert **partitioned** Hive tables (orc/parquet) to data source tables in the write path, but the read path is using the metadata cache for both **partitioned** and non-partitioned Hive tables (orc/parquet). That means, writing the partitioned parquet/orc tables still use `InsertIntoHiveTable`, instead of `InsertIntoHadoopFsRelationCommand`. To avoid reading the out-of-dated cache, `InsertIntoHiveTable` needs to refresh the metadata cache for partitioned tables. Note, it does not need to refresh the cache for non-partitioned parquet/orc tables, because it does not call `InsertIntoHiveTable` at all. Based on the comments, this PR will keep the existing logics unchanged. That means, we always refresh the table no matter whether the table is partitioned or not.

### How was this patch tested?
Added test cases in parquetSuites.scala

Author: gatorsmile <gatorsmile@gmail.com>

Closes #16500 from gatorsmile/refreshInsertIntoHiveTable.

## What changes were proposed in this pull request?

Fix outdated parameter descriptions in kafka010

## How was this patch tested?

cc koeninger  zsxwing

Author: uncleGen <hustyugm@gmail.com>

Closes #16569 from uncleGen/SPARK-19206.

## What changes were proposed in this pull request?

Upgrade Netty to `4.0.43.Final` to add the fix for https://github.com/netty/netty/issues/6153

## How was this patch tested?

Jenkins

Author: Shixiong Zhu <shixiong@databricks.com>

Closes #16568 from zsxwing/SPARK-18971.

## What changes were proposed in this pull request?

core/src/main/scala/org/apache/spark/SparkContext.scala contains LOCAL_N_FAILURES_REGEX master mode, but this was never documented, so do so.

## How was this patch tested?

By using the Github Markdown preview feature.

Author: Maurus Cuelenaere <mcuelenaere@gmail.com>

Closes #16562 from mcuelenaere/patch-1.

[SPARK-19042] spark executor can't download the jars when uber jar's http url contains any query strings

If the uber jars' https contains any query strings, the Executor.updateDependencies method can't can't download the jars correctly. This is because  the "localName = name.split("/").last" won't get the expected jar's url. The bug fix is the same as [SPARK-17855]

Author: xiaojian.fxj <xiaojian.fxj@alibaba-inc.com>

Closes #16509 from hustfxj/bug.

## What changes were proposed in this pull request?

Using Slf4JLoggerFactory.INSTANCE instead of creating Slf4JLoggerFactory's object with constructor. It's deprecated.

## How was this patch tested?

With running StateStoreRDDSuite.

Author: Tsuyoshi Ozawa <ozawa@apache.org>

Closes #16570 from oza/SPARK-19207.

## What changes were proposed in this pull request?

After [SPARK-19107](https://issues.apache.org/jira/browse/SPARK-19107), we now can treat hive as a data source and create hive tables with DataFrameWriter and Catalog. However, the support is not completed, there are still some cases we do not support.

This PR implement:
DataFrameWriter.saveAsTable work with hive format with overwrite mode

## How was this patch tested?
unit test added

Author: windpiger <songjun@outlook.com>

Closes #16549 from windpiger/saveAsTableWithHiveOverwrite.

[SPARK-19221][PROJECT INFRA][R] Add winutils binaries to the path in AppVeyor tests for Hadoop libraries to call native codes properly

## What changes were proposed in this pull request?

It seems Hadoop libraries need winutils binaries for native libraries in the path.

It is not a problem in tests for now because we are only testing SparkR on Windows via AppVeyor but it can be a problem if we run Scala tests via AppVeyor as below:

```
 - SPARK-18220: read Hive orc table with varchar column *** FAILED *** (3 seconds, 937 milliseconds)
   org.apache.spark.sql.execution.QueryExecutionException: FAILED: Execution Error, return code -101 from org.apache.hadoop.hive.ql.exec.mr.MapRedTask. org.apache.hadoop.io.nativeio.NativeIO$Windows.access0(Ljava/lang/String;I)Z
   at org.apache.spark.sql.hive.client.HiveClientImpl$$anonfun$runHive$1.apply(HiveClientImpl.scala:625)
   at org.apache.spark.sql.hive.client.HiveClientImpl$$anonfun$runHive$1.apply(HiveClientImpl.scala:609)
   at org.apache.spark.sql.hive.client.HiveClientImpl$$anonfun$withHiveState$1.apply(HiveClientImpl.scala:283)
   ...
```

This PR proposes to add it to the `Path` for AppVeyor tests.

## How was this patch tested?

Manually via AppVeyor.

**Before**
https://ci.appveyor.com/project/spark-test/spark/build/549-windows-complete/job/gc8a1pjua2bc4i8m

**After**
https://ci.appveyor.com/project/spark-test/spark/build/572-windows-complete/job/c4vrysr5uvj2hgu7

Author: hyukjinkwon <gurwls223@gmail.com>

Closes #16584 from HyukjinKwon/set-path-appveyor.

## What changes were proposed in this pull request?

the offset of short is 4 in OffHeapColumnVector's putShorts, but actually it should be 2.

## How was this patch tested?

unit test

Author: Yucai Yu <yucai.yu@intel.com>

Closes #16555 from yucai/offheap_short.

## What changes were proposed in this pull request?

To allow specifying number of partitions when the DataFrame is created

## How was this patch tested?

manual, unit tests

Author: Felix Cheung <felixcheung_m@hotmail.com>

Closes #16512 from felixcheung/rnumpart.

[SPARK-18687][PYSPARK][SQL] Backward compatibility - creating a Dataframe on a new SQLContext object fails with a Derby error

Change is for SQLContext to reuse the active SparkSession during construction if the sparkContext supplied is the same as the currently active SparkContext. Without this change, a new SparkSession is instantiated that results in a Derby error when attempting to create a dataframe using a new SQLContext object even though the SparkContext supplied to the new SQLContext is same as the currently active one. Refer https://issues.apache.org/jira/browse/SPARK-18687 for details on the error and a repro.

Existing unit tests and a new unit test added to pyspark-sql:

/python/run-tests --python-executables=python --modules=pyspark-sql

Please review http://spark.apache.org/contributing.html before opening a pull request.

Author: Vinayak <vijoshi5@in.ibm.com>
Author: Vinayak Joshi <vijoshi@users.noreply.github.com>

Closes #16119 from vijoshi/SPARK-18687_master.

Otherwise the open parentheses isn't closed in query plan descriptions of batch scans.

    PushedFilters: [In(COL_A, [1,2,4,6,10,16,219,815], IsNotNull(COL_B), ...

Author: Andrew Ash <andrew@andrewash.com>

Closes #16558 from ash211/patch-9.

## What changes were proposed in this pull request?

When we convert a string to integral, we will convert that string to `decimal(20, 0)` first, so that we can turn a string with decimal format to truncated integral, e.g. `CAST('1.2' AS int)` will return `1`.

However, this brings problems when we convert a string with large numbers to integral, e.g. `CAST('1234567890123' AS int)` will return `1912276171`, while Hive returns null as we expected.

This is a long standing bug(seems it was there the first day Spark SQL was created), this PR fixes this bug by adding the native support to convert `UTF8String` to integral.

## How was this patch tested?

new regression tests

Author: Wenchen Fan <wenchen@databricks.com>

Closes #16550 from cloud-fan/string-to-int.

## What changes were proposed in this pull request?
spark.kmeans doesn't have interface to set initSteps, seed and tol. As Spark Kmeans algorithm doesn't take the same set of parameters as R kmeans, we should maintain a different interface in spark.kmeans.

Add missing parameters and corresponding document.

Modified existing unit tests to take additional parameters.

Author: wm624@hotmail.com <wm624@hotmail.com>

Closes #16523 from wangmiao1981/kmeans.

### What changes were proposed in this pull request?
`DataFrameWriter`'s [save() API](https://github.com/gatorsmile/spark/blob/5d38f09f47a767a342a0a8219c63efa2943b5d1f/sql/core/src/main/scala/org/apache/spark/sql/DataFrameWriter.scala#L207) is performing a unnecessary full filesystem scan for the saved files. The save() API is the most basic/core API in `DataFrameWriter`. We should avoid it.

The related PR: https://github.com/apache/spark/pull/16090

### How was this patch tested?
Updated the existing test cases.

Author: gatorsmile <gatorsmile@gmail.com>

Closes #16481 from gatorsmile/saveFileScan.

[SPARK-19110][MLLIB][FOLLOWUP] Add a unit test for testing logPrior and logLikelihood of DistributedLDAModel in MLLIB

## What changes were proposed in this pull request?
#16491 added the fix to mllib and a unit test to ml. This followup PR, add unit tests to mllib suite.

## How was this patch tested?
Unit tests.

Author: wm624@hotmail.com <wm624@hotmail.com>

Closes #16524 from wangmiao1981/ldabug.

## What changes were proposed in this pull request?
Pivoting adds backticks (e.g. 3_count(\`c\`)) in column names and, in some cases,
thes causes analysis exceptions  like;
```
scala> val df = Seq((2, 3, 4), (3, 4, 5)).toDF("a", "x", "y")
scala> df.groupBy("a").pivot("x").agg(count("y"), avg("y")).na.fill(0)
org.apache.spark.sql.AnalysisException: syntax error in attribute name: `3_count(`y`)`;
  at org.apache.spark.sql.catalyst.analysis.UnresolvedAttribute$.e$1(unresolved.scala:134)
  at org.apache.spark.sql.catalyst.analysis.UnresolvedAttribute$.parseAttributeName(unresolved.scala:144)
...
```
So, this pr proposes to remove these backticks from column names.

## How was this patch tested?
Added a test in `DataFrameAggregateSuite`.

Author: Takeshi YAMAMURO <linguin.m.s@gmail.com>

Closes #14812 from maropu/SPARK-17237.

## What changes were proposed in this pull request?

lower "block locks were not released" log to info level, as it is generating a lot of warnings in running ML, graph calls, as pointed out in the JIRA.

Author: Felix Cheung <felixcheung_m@hotmail.com>

Closes #16513 from felixcheung/blocklockswarn.

## What changes were proposed in this pull request?

In SparkSession initialization, we store created the instance of SparkSession into a class variable _instantiatedContext. Next time we can use SparkSession.builder.getOrCreate() to retrieve the existing SparkSession instance.

However, when the active SparkContext is stopped and we create another new SparkContext to use, the existing SparkSession is still associated with the stopped SparkContext. So the operations with this existing SparkSession will be failed.

We need to detect such case in SparkSession and renew the class variable _instantiatedContext if needed.

## How was this patch tested?

New test added in PySpark.

Please review http://spark.apache.org/contributing.html before opening a pull request.

Author: Liang-Chi Hsieh <viirya@gmail.com>

Closes #16454 from viirya/fix-pyspark-sparksession.

## What changes were proposed in this pull request?

Currently nondeterministic expressions are allowed in `Aggregate`(see the [comment](https://github.com/apache/spark/blob/v2.0.2/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/CheckAnalysis.scala#L249-L251)), but the `PullOutNondeterministic` analyzer rule failed to handle `Aggregate`, this PR fixes it.

close https://github.com/apache/spark/pull/16379

There is still one remaining issue: `SELECT a + rand() FROM t GROUP BY a + rand()` is not allowed, because the 2 `rand()` are different(we generate random seed as the default seed for `rand()`). https://issues.apache.org/jira/browse/SPARK-19035 is tracking this issue.

## How was this patch tested?

a new test suite

Author: Wenchen Fan <wenchen@databricks.com>

Closes #16404 from cloud-fan/groupby.

## What changes were proposed in this pull request?

Currently in SQL we implement overwrites by calling fs.delete() directly on the original data. This is not ideal since we the original files end up deleted even if the job aborts. We should extend the commit protocol to allow file overwrites to be managed as well.

## How was this patch tested?

Existing tests. I also fixed a bunch of tests that were depending on the commit protocol implementation being set to the legacy mapreduce one.

cc rxin cloud-fan

Author: Eric Liang <ekl@databricks.com>
Author: Eric Liang <ekhliang@gmail.com>

Closes #16554 from ericl/add-delete-protocol.

## What changes were proposed in this pull request?

Removes `UserDefinedFunction._broadcast` and `UserDefinedFunction.__del__` method.

## How was this patch tested?

Existing unit tests.

Author: zero323 <zero323@users.noreply.github.com>

Closes #16538 from zero323/SPARK-19164.

## What changes were proposed in this pull request?
```ml.R``` example depends on ```e1071``` package, if it's not available in users' environment, it will fail. I think the example should not depends on third-party packages, so I update it to remove the dependency.

## How was this patch tested?
Manual test.

Author: Yanbo Liang <ybliang8@gmail.com>

Closes #16548 from yanboliang/spark-19158.

## What changes were proposed in this pull request?

This PR proposes to throw an exception for both jdbc APIs when user specified schemas are not allowed or useless.

**DataFrameReader.jdbc(...)**

``` scala
spark.read.schema(StructType(Nil)).jdbc(...)
```

**DataFrameReader.table(...)**

```scala
spark.read.schema(StructType(Nil)).table("usrdb.test")
```

## How was this patch tested?

Unit test in `JDBCSuite` and `DataFrameReaderWriterSuite`.

Author: hyukjinkwon <gurwls223@gmail.com>

Closes #14451 from HyukjinKwon/SPARK-16848.

## What changes were proposed in this pull request?

In this pr, we add more test cases for project and aggregate estimation.

## How was this patch tested?

Add test cases.

Author: wangzhenhua <wangzhenhua@huawei.com>

Closes #16551 from wzhfy/addTests.