#### What changes were proposed in this pull request?
Ensure that all built-in expressions can be mapped to its SQL representation if there is one (e.g. ScalaUDF doesn't have a SQL representation). The function lists are from the expression list in `FunctionRegistry`.
window functions, grouping sets functions (`cube`, `rollup`, `grouping`, `grouping_id`), generator functions (`explode` and `json_tuple`) are covered by separate JIRA and PRs. Thus, this PR does not cover them. Except these functions, all the built-in expressions are covered. For details, see the list in `ExpressionToSQLSuite`.
Fixed a few issues. For example, the `prettyName` of `approx_count_distinct` is not right. The `sql` of `hash` function is not right, since the `hash` function does not accept `seed`.
Additionally, also correct the order of expressions in `FunctionRegistry` so that people are easier to find which functions are missing.
cc liancheng
#### How was the this patch tested?
Added two test cases in LogicalPlanToSQLSuite for covering `not like` and `not in`.
Added a new test suite `ExpressionToSQLSuite` to cover the functions:
1. misc non-aggregate functions + complex type creators + null expressions
2. math functions
3. aggregate functions
4. string functions
5. date time functions + calendar interval
6. collection functions
7. misc functions
Author: gatorsmile <gatorsmile@gmail.com>
Closes#11314 from gatorsmile/expressionToSQL.
In SparkSQLCLI, we have created a `CliSessionState`, but then we call `SparkSQLEnv.init()`, which will start another `SessionState`. This would lead to exception because `processCmd` need to get the `CliSessionState` instance by calling `SessionState.get()`, but the return value would be a instance of `SessionState`. See the exception below.
spark-sql> !echo "test";
Exception in thread "main" java.lang.ClassCastException: org.apache.hadoop.hive.ql.session.SessionState cannot be cast to org.apache.hadoop.hive.cli.CliSessionState
at org.apache.hadoop.hive.cli.CliDriver.processCmd(CliDriver.java:112)
at org.apache.spark.sql.hive.thriftserver.SparkSQLCLIDriver.processCmd(SparkSQLCLIDriver.scala:301)
at org.apache.hadoop.hive.cli.CliDriver.processLine(CliDriver.java:376)
at org.apache.spark.sql.hive.thriftserver.SparkSQLCLIDriver$.main(SparkSQLCLIDriver.scala:242)
at org.apache.spark.sql.hive.thriftserver.SparkSQLCLIDriver.main(SparkSQLCLIDriver.scala)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.apache.spark.deploy.SparkSubmit$.org$apache$spark$deploy$SparkSubmit$$runMain(SparkSubmit.scala:691)
at org.apache.spark.deploy.SparkSubmit$.doRunMain$1(SparkSubmit.scala:180)
at org.apache.spark.deploy.SparkSubmit$.submit(SparkSubmit.scala:205)
at org.apache.spark.deploy.SparkSubmit$.main(SparkSubmit.scala:120)
at org.apache.spark.deploy.SparkSubmit.main(SparkSubmit.scala)
Author: Daoyuan Wang <daoyuan.wang@intel.com>
Closes#9589 from adrian-wang/clicommand.
## What changes were proposed in this pull request?
When there are some special characters (e.g., `"`, `\`) in `label`, DAG will be broken. This patch just escapes `label` to avoid DAG being broken by some special characters
## How was the this patch tested?
Jenkins tests
Author: Shixiong Zhu <shixiong@databricks.com>
Closes#11309 from zsxwing/SPARK-13298.
As also mentioned/marked by TODO in AFTAggregator.AFTAggregator.add(data: AFTPoint) method a new array is being created for intercept value and it is being concatenated
with another array which contains the betas, the resulted Array is being converted into a Dense vector which in its turn is being converted into breeze vector.
This is expensive and not necessarily beautiful.
I've tried to solve above mentioned problem by simple algebraic decompositions - keeping and treating intercept independently.
Please let me know what do you think and if you have any questions.
Thanks,
Narine
Author: Narine Kokhlikyan <narine.kokhlikyan@gmail.com>
Closes#11179 from NarineK/survivaloptim.
Replaced example example code in mllib-dimensionality-reduction.md using
include_example
Author: Devaraj K <devaraj@apache.org>
Closes#11132 from devaraj-kavali/SPARK-13016.
Use the HashedRelation which is a more optimized datastructure and reduce code complexity
Author: Xiu Guo <xguo27@gmail.com>
Closes#11291 from xguo27/SPARK-13422.
A common problem that users encounter with Spark 1.6.0 is that writing to a partitioned parquet table OOMs. The root cause is that parquet allocates a significant amount of memory that is not accounted for by our own mechanisms. As a workaround, we can ensure that only a single file is open per task unless the user explicitly asks for more.
Author: Michael Armbrust <michael@databricks.com>
Closes#11308 from marmbrus/parquetWriteOOM.
## What changes were proposed in this pull request?
This patch removes SparkContext.metricsSystem. SparkContext.metricsSystem returns MetricsSystem, which is a private class. I think it was added by accident.
In addition, I also removed an unused private[spark] method schedulerBackend setter.
## How was the this patch tested?
N/A.
Author: Reynold Xin <rxin@databricks.com>
This patch had conflicts when merged, resolved by
Committer: Josh Rosen <joshrosen@databricks.com>
Closes#11282 from rxin/SPARK-13413.
Currently the Mesos cluster dispatcher is not using offers from multiple roles correctly, as it simply aggregates all the offers resource values into one, but doesn't apply them correctly before calling the driver as Mesos needs the resources from the offers to be specified which role it originally belongs to. Multiple roles is already supported with fine/coarse grain scheduler, so porting that logic here to the cluster scheduler.
https://issues.apache.org/jira/browse/SPARK-10749
Author: Timothy Chen <tnachen@gmail.com>
Closes#8872 from tnachen/cluster_multi_roles.
ML ```KMeansModel / BisectingKMeansModel / QuantileDiscretizer``` should set parent.
cc mengxr
Author: Yanbo Liang <ybliang8@gmail.com>
Closes#11214 from yanboliang/spark-13334.
Part of task for [SPARK-11219](https://issues.apache.org/jira/browse/SPARK-11219) to make PySpark MLlib parameter description formatting consistent. This is for the fpm and recommendation modules.
Closes#10602Closes#10897
Author: Bryan Cutler <cutlerb@gmail.com>
Author: somideshmukh <somilde@us.ibm.com>
Closes#11186 from BryanCutler/param-desc-consistent-fpmrecc-SPARK-12632.
## What changes were proposed in this pull request?
This PR tries to fix all typos in all markdown files under `docs` module,
and fixes similar typos in other comments, too.
## How was the this patch tested?
manual tests.
Author: Dongjoon Hyun <dongjoon@apache.org>
Closes#11300 from dongjoon-hyun/minor_fix_typos.
## What changes were proposed in this pull request?
Change the checkpointsuite getting the outputstreams to explicitly be unchecked on the generic type so as to avoid the warnings. This only impacts test code.
Alternatively we could encode the type tag in the TestOutputStreamWithPartitions and filter the type tag as well - but this is unnecessary since multiple testoutputstreams are not registered and the previous code was not actually checking this type.
## How was the this patch tested?
unit tests (streaming/testOnly org.apache.spark.streaming.CheckpointSuite)
Author: Holden Karau <holden@us.ibm.com>
Closes#11286 from holdenk/SPARK-13399-checkpointsuite-type-erasure.
add support of arbitrary length sentence by using the nature representation of sentences in the input.
add new similarity functions and add normalization option for distances in synonym finding
add new accessor for internal structure(the vocabulary and wordindex) for convenience
need instructions about how to set value for the Since annotation for newly added public functions. 1.5.3?
jira link: https://issues.apache.org/jira/browse/SPARK-12153
Author: Yong Gang Cao <ygcao@amazon.com>
Author: Yong-Gang Cao <ygcao@users.noreply.github.com>
Closes#10152 from ygcao/improvementForSentenceBoundary.
trait SynchronizedMap in package mutable is deprecated: Synchronization via traits is deprecated as it is inherently unreliable. Change to java.util.concurrent.ConcurrentHashMap instead.
Author: Huaxin Gao <huaxing@us.ibm.com>
Closes#11250 from huaxingao/spark__13186.
## What changes were proposed in this pull request?
This PR removes the support of SIMR, since SIMR is not actively used and maintained for a long time, also is not supported from `SparkSubmit`, so here propose to remove it.
## How was the this patch tested?
This patch is tested locally by running unit tests.
Author: jerryshao <sshao@hortonworks.com>
Closes#11296 from jerryshao/SPARK-13426.
## What changes were proposed in this pull request?
Fix MLlib LogisticRegressionWithLBFGS regularization map as:
```SquaredL2Updater``` -> ```elasticNetParam = 0.0```
```L1Updater``` -> ```elasticNetParam = 1.0```
cc dbtsai
## How was the this patch tested?
unit tests
Author: Yanbo Liang <ybliang8@gmail.com>
Closes#11258 from yanboliang/spark-13379.
https://issues.apache.org/jira/browse/SPARK-13381
This PR adds the support to load CSV data directly by a single call with given paths.
Also, I corrected this to refer all paths rather than the first path in schema inference, which JSON datasource dose.
Several unitests were added for each functionality.
Author: hyukjinkwon <gurwls223@gmail.com>
Closes#11262 from HyukjinKwon/SPARK-13381.
JIRA: https://issues.apache.org/jira/browse/SPARK-13321
The following SQL can not be parsed with current parser:
SELECT `u_1`.`id` FROM (((SELECT `t0`.`id` FROM `default`.`t0`) UNION ALL (SELECT `t0`.`id` FROM `default`.`t0`)) UNION ALL (SELECT `t0`.`id` FROM `default`.`t0`)) AS u_1
We should fix it.
Author: Liang-Chi Hsieh <viirya@gmail.com>
Closes#11204 from viirya/nested-union.
jegonzal ankurdave please could you review
## What changes were proposed in this pull request?
Reworking of jegonzal PR #2495 to address the issue identified in SPARK-3650. Code amended to use the convertToCanonicalEdges method.
## How was the this patch tested?
Patch was tested using the unit tests created in PR #2495
Author: Robin East <robin.east@xense.co.uk>
Author: Joseph E. Gonzalez <joseph.e.gonzalez@gmail.com>
Closes#11290 from insidedctm/spark-3650.
## What changes were proposed in this pull request?
This PR adds equality operators to UDT classes so that they can be correctly tested for dataType equality during union operations.
This was previously causing `"AnalysisException: u"unresolved operator 'Union;""` when trying to unionAll two dataframes with UDT columns as below.
```
from pyspark.sql.tests import PythonOnlyPoint, PythonOnlyUDT
from pyspark.sql import types
schema = types.StructType([types.StructField("point", PythonOnlyUDT(), True)])
a = sqlCtx.createDataFrame([[PythonOnlyPoint(1.0, 2.0)]], schema)
b = sqlCtx.createDataFrame([[PythonOnlyPoint(3.0, 4.0)]], schema)
c = a.unionAll(b)
```
## How was the this patch tested?
Tested using two unit tests in sql/test.py and the DataFrameSuite.
Additional information here : https://issues.apache.org/jira/browse/SPARK-13410
Author: Franklyn D'souza <franklynd@gmail.com>
Closes#11279 from damnMeddlingKid/udt-union-all.
## What changes were proposed in this pull request?
Fixed the test failure `org.apache.spark.sql.util.ContinuousQueryListenerSuite.event ordering`: https://amplab.cs.berkeley.edu/jenkins/job/spark-master-test-maven-hadoop-2.6/202/testReport/junit/org.apache.spark.sql.util/ContinuousQueryListenerSuite/event_ordering/
```
org.scalatest.exceptions.TestFailedException:
Assert failed: : null equaled null onQueryTerminated called before onQueryStarted
org.scalatest.Assertions$class.newAssertionFailedException(Assertions.scala:500)
org.scalatest.FunSuite.newAssertionFailedException(FunSuite.scala:1555)
org.scalatest.Assertions$AssertionsHelper.macroAssert(Assertions.scala:466)
org.apache.spark.sql.util.ContinuousQueryListenerSuite$QueryStatusCollector$$anonfun$onQueryTerminated$1.apply$mcV$sp(ContinuousQueryListenerSuite.scala:204)
org.scalatest.concurrent.AsyncAssertions$Waiter.apply(AsyncAssertions.scala:349)
org.apache.spark.sql.util.ContinuousQueryListenerSuite$QueryStatusCollector.onQueryTerminated(ContinuousQueryListenerSuite.scala:203)
org.apache.spark.sql.execution.streaming.ContinuousQueryListenerBus.doPostEvent(ContinuousQueryListenerBus.scala:67)
org.apache.spark.sql.execution.streaming.ContinuousQueryListenerBus.doPostEvent(ContinuousQueryListenerBus.scala:32)
org.apache.spark.util.ListenerBus$class.postToAll(ListenerBus.scala:63)
org.apache.spark.sql.execution.streaming.ContinuousQueryListenerBus.postToAll(ContinuousQueryListenerBus.scala:32)
```
In the previous codes, when the test `adding and removing listener` finishes, there may be still some QueryTerminated events in the listener bus queue. Then when `event ordering` starts to run, it may see these events and throw the above exception.
This PR just added `waitUntilEmpty` in `after` to make sure all events be consumed after each test.
## How was the this patch tested?
Jenkins tests.
Author: Shixiong Zhu <shixiong@databricks.com>
Closes#11275 from zsxwing/SPARK-13405.
## What changes were proposed in this pull request?
This PR fixes some typos in the following documentation files.
* `NOTICE`, `configuration.md`, and `hardware-provisioning.md`.
## How was the this patch tested?
manual tests
Author: Dongjoon Hyun <dongjoonapache.org>
Author: Dongjoon Hyun <dongjoon@apache.org>
Closes#11289 from dongjoon-hyun/minor_fix_typos_notice_and_confdoc.
## What changes were proposed in this pull request?
This is a step towards merging `SQLContext` and `HiveContext`. A new internal Catalog API was introduced in #10982 and extended in #11069. This patch introduces an implementation of this API using `HiveClient`, an existing interface to Hive. It also extends `HiveClient` with additional calls to Hive that are needed to complete the catalog implementation.
*Where should I start reviewing?* The new catalog introduced is `HiveCatalog`. This class is relatively simple because it just calls `HiveClientImpl`, where most of the new logic is. I would not start with `HiveClient`, `HiveQl`, or `HiveMetastoreCatalog`, which are modified mainly because of a refactor.
*Why is this patch so big?* I had to refactor HiveClient to remove an intermediate representation of databases, tables, partitions etc. After this refactor `CatalogTable` convert directly to and from `HiveTable` (etc.). Otherwise we would have to first convert `CatalogTable` to the intermediate representation and then convert that to HiveTable, which is messy.
The new class hierarchy is as follows:
```
org.apache.spark.sql.catalyst.catalog.Catalog
- org.apache.spark.sql.catalyst.catalog.InMemoryCatalog
- org.apache.spark.sql.hive.HiveCatalog
```
Note that, as of this patch, none of these classes are currently used anywhere yet. This will come in the future before the Spark 2.0 release.
## How was the this patch tested?
All existing unit tests, and HiveCatalogSuite that extends CatalogTestCases.
Author: Andrew Or <andrew@databricks.com>
Author: Reynold Xin <rxin@databricks.com>
Closes#11293 from rxin/hive-catalog.
https://issues.apache.org/jira/browse/SPARK-13137
This PR adds a filter in schema inference so that it does not emit NullPointException.
Also, I removed `MAX_COMMENT_LINES_IN_HEADER `but instead used a monad chaining with `filter()` and `first()`.
Lastly, I simply added a newline rather than adding a new file for this so that this is covered with the original tests.
Author: hyukjinkwon <gurwls223@gmail.com>
Closes#11023 from HyukjinKwon/SPARK-13137.
Quite a few Spark SQL join operators broadcast one side of the join to all nodes. The are a few problems with this:
- This conflates broadcasting (a data exchange) with joining. Data exchanges should be managed by a different operator.
- All these nodes implement their own (duplicate) broadcasting logic.
- Re-use of indices is quite hard.
This PR defines both a ```BroadcastDistribution``` and ```BroadcastPartitioning```, these contain a `BroadcastMode`. The `BroadcastMode` defines the way in which we transform the Array of `InternalRow`'s into an index. We currently support the following `BroadcastMode`'s:
- IdentityBroadcastMode: This broadcasts the rows in their original form.
- HashSetBroadcastMode: This applies a projection to the input rows, deduplicates these rows and broadcasts the resulting `Set`.
- HashedRelationBroadcastMode: This transforms the input rows into a `HashedRelation`, and broadcasts this index.
To match this distribution we implement a ```BroadcastExchange``` operator which will perform the broadcast for us, and have ```EnsureRequirements``` plan this operator. The old Exchange operator has been renamed into ShuffleExchange in order to clearly separate between Shuffled and Broadcasted exchanges. Finally the classes in Exchange.scala have been moved to a dedicated package.
cc rxin davies
Author: Herman van Hovell <hvanhovell@questtec.nl>
Closes#11083 from hvanhovell/SPARK-13136.
## What changes were proposed in this pull request?
This pull request fixes some minor issues (documentation, test flakiness, test organization) with #11190, which was merged earlier tonight.
## How was the this patch tested?
unit tests.
Author: Reynold Xin <rxin@databricks.com>
Closes#11285 from rxin/subquery.
## What changes were proposed in this pull request?
This patch renames logical.Subquery to logical.SubqueryAlias, which is a more appropriate name for this operator (versus subqueries as expressions).
## How was the this patch tested?
Unit tests.
Author: Reynold Xin <rxin@databricks.com>
Closes#11288 from rxin/SPARK-13420.
This PR introduces several major changes:
1. Replacing `Expression.prettyString` with `Expression.sql`
The `prettyString` method is mostly an internal, developer faced facility for debugging purposes, and shouldn't be exposed to users.
1. Using SQL-like representation as column names for selected fields that are not named expression (back-ticks and double quotes should be removed)
Before, we were using `prettyString` as column names when possible, and sometimes the result column names can be weird. Here are several examples:
Expression | `prettyString` | `sql` | Note
------------------ | -------------- | ---------- | ---------------
`a && b` | `a && b` | `a AND b` |
`a.getField("f")` | `a[f]` | `a.f` | `a` is a struct
1. Adding trait `NonSQLExpression` extending from `Expression` for expressions that don't have a SQL representation (e.g. Scala UDF/UDAF and Java/Scala object expressions used for encoders)
`NonSQLExpression.sql` may return an arbitrary user facing string representation of the expression.
Author: Cheng Lian <lian@databricks.com>
Closes#10757 from liancheng/spark-12799.simplify-expression-string-methods.
JIRA: https://issues.apache.org/jira/browse/SPARK-13416
## What changes were proposed in this pull request?
The output of StronglyConnectedComponents with numIter no greater than 1 may make no sense. So I just add require check in it.
## How was the this patch tested?
unit tests passed
Author: Zheng RuiFeng <ruifengz@foxmail.com>
Closes#11284 from zhengruifeng/scccheck.
```scala
// case 1: missing sort columns are resolvable if join is true
sql("SELECT explode(a) AS val, b FROM data WHERE b < 2 order by val, c")
// case 2: missing sort columns are not resolvable if join is false. Thus, issue an error message in this case
sql("SELECT explode(a) AS val FROM data order by val, c")
```
When sort columns are not in `Generate`, we can resolve them when `join` is equal to `true`. Still trying to add more test cases for the other `UnaryNode` types.
Could you review the changes? davies cloud-fan Thanks!
Author: gatorsmile <gatorsmile@gmail.com>
Closes#11198 from gatorsmile/missingInSort.
## What changes were proposed in this pull request?
Users might want to start multiple mesos dispatchers, as each dispatcher can potentially be part of different roles and used for multi-tenancy.
To allow multiple Mesos dispatchers to be launched, we need to be able to specify a instance number when starting the dispatcher daemon.
## How was the this patch tested?
Manual testing
Author: Timothy Chen <tnachen@gmail.com>
Closes#11281 from tnachen/multiple_cluster_dispatchers.
JIRA: https://issues.apache.org/jira/browse/SPARK-13386
## What changes were proposed in this pull request?
add maxIteration option for ConnectedComponents algorithm
## How was the this patch tested?
unit tests passed
Author: Zheng RuiFeng <ruifengz@foxmail.com>
Closes#11268 from zhengruifeng/ccwithmax.
Some of the new doctests in ml/clustering.py have a lot of setup code, move the setup code to the general test init to keep the doctest more example-style looking.
In part this is a follow up to https://github.com/apache/spark/pull/10999
Note that the same pattern is followed in regression & recommendation - might as well clean up all three at the same time.
Author: Holden Karau <holden@us.ibm.com>
Closes#11197 from holdenk/SPARK-13302-cleanup-doctests-in-ml-clustering.
## What changes were proposed in this pull request?
`JobWaiter.taskSucceeded` will be called for each task. When `resultHandler` throws an exception, `taskSucceeded` will also throw it for each task. DAGScheduler just catches it and reports it like this:
```Scala
try {
job.listener.taskSucceeded(rt.outputId, event.result)
} catch {
case e: Exception =>
// TODO: Perhaps we want to mark the resultStage as failed?
job.listener.jobFailed(new SparkDriverExecutionException(e))
}
```
Therefore `JobWaiter.jobFailed` may be called multiple times.
So `JobWaiter.jobFailed` should use `Promise.tryFailure` instead of `Promise.failure` because the latter one doesn't support calling multiple times.
## How was the this patch tested?
Jenkins tests.
Author: Shixiong Zhu <shixiong@databricks.com>
Closes#11280 from zsxwing/SPARK-13408.
Conversion of outer joins, if the predicates in filter conditions can restrict the result sets so that all null-supplying rows are eliminated.
- `full outer` -> `inner` if both sides have such predicates
- `left outer` -> `inner` if the right side has such predicates
- `right outer` -> `inner` if the left side has such predicates
- `full outer` -> `left outer` if only the left side has such predicates
- `full outer` -> `right outer` if only the right side has such predicates
If applicable, this can greatly improve the performance, since outer join is much slower than inner join, full outer join is much slower than left/right outer join.
The original PR is https://github.com/apache/spark/pull/10542
Author: gatorsmile <gatorsmile@gmail.com>
Author: xiaoli <lixiao1983@gmail.com>
Author: Xiao Li <xiaoli@Xiaos-MacBook-Pro.local>
Closes#10567 from gatorsmile/outerJoinEliminationByFilterCond.
`TaskMetrics.fromAccumulatorUpdates()` can fail if accumulators have been garbage-collected on the driver. To guard against this, this patch introduces `ListenerTaskMetrics`, a subclass of `TaskMetrics` which is used only in `TaskMetrics.fromAccumulatorUpdates()` and which eliminates the need to access the original accumulators on the driver.
Author: Josh Rosen <joshrosen@databricks.com>
Closes#11276 from JoshRosen/accum-updates-fix.
This PR adds support for rewriting constraints if there are aliases in the query plan. For e.g., if there is a query of form `SELECT a, a AS b`, any constraints on `a` now also apply to `b`.
JIRA: https://issues.apache.org/jira/browse/SPARK-13091
cc marmbrus
Author: Sameer Agarwal <sameer@databricks.com>
Closes#11144 from sameeragarwal/alias.
This patch expose `maxCharactersPerColumn` and `maxColumns` to user in CSV data source.
Author: Hossein <hossein@databricks.com>
Closes#11147 from falaki/SPARK-13261.
Fixes error `org.postgresql.util.PSQLException: Unable to find server array type for provided name decimal(38,18)`.
* Passes scale metadata to JDBC dialect for usage in type conversions.
* Removes unused length/scale/precision parameters from `createArrayOf` parameter `typeName` (for writing).
* Adds configurable precision and scale to Postgres `DecimalType` (for reading).
* Adds a new kind of test that verifies the schema written by `DataFrame.write.jdbc`.
Author: Brandon Bradley <bradleytastic@gmail.com>
Closes#10928 from blbradley/spark-12966.
JIRA: https://issues.apache.org/jira/browse/SPARK-13384
## What changes were proposed in this pull request?
When we de-duplicate attributes in Analyzer, we create new attributes. However, we don't keep original qualifiers. Some plans will be failed to analysed. We should keep original qualifiers in new attributes.
## How was the this patch tested?
Unit test is added.
Author: Liang-Chi Hsieh <viirya@gmail.com>
Closes#11261 from viirya/keep-attr-qualifiers.
## What changes were proposed in this pull request?
Clarify that 0.21 is only a **minimum** requirement.
## How was the this patch tested?
It's a doc change, so no tests.
Author: Iulian Dragos <jaguarul@gmail.com>
Closes#11271 from dragos/patch-1.
Clarify that reduce functions need to be commutative, and fold functions do not
See https://github.com/apache/spark/pull/11091
Author: Sean Owen <sowen@cloudera.com>
Closes#11217 from srowen/SPARK-13339.