Apache Spark - A unified analytics engine for large-scale data processing
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Wenchen Fan e853afb416 [SPARK-26448][SQL] retain the difference between 0.0 and -0.0
## What changes were proposed in this pull request?

In https://github.com/apache/spark/pull/23043 , we introduced a behavior change: Spark users are not able to distinguish 0.0 and -0.0 anymore.

This PR proposes an alternative fix to the original bug, to retain the difference between 0.0 and -0.0 inside Spark.

The idea is, we can rewrite the window partition key, join key and grouping key during logical phase, to normalize the special floating numbers. Thus only operators care about special floating numbers need to pay the perf overhead, and end users can distinguish -0.0.

## How was this patch tested?

existing test

Closes #23388 from cloud-fan/minor.

Authored-by: Wenchen Fan <wenchen@databricks.com>
Signed-off-by: gatorsmile <gatorsmile@gmail.com>
2019-01-09 13:50:32 -08:00
.github [SPARK-18073][DOCS][WIP] Migrate wiki to spark.apache.org web site 2016-11-23 11:25:47 +00:00
assembly [SPARK-26134][CORE] Upgrading Hadoop to 2.7.4 to fix java.version problem 2018-11-21 23:09:57 -08:00
bin [SPARK-26083][K8S] Add Copy pyspark into corresponding dir cmd in pyspark Dockerfile 2018-12-03 15:36:41 -08:00
build [SPARK-26144][BUILD] build/mvn should detect scala.version based on scala.binary.version 2018-11-22 14:49:41 -08:00
common [SPARK-24920][CORE] Allow sharing Netty's memory pool allocators 2019-01-08 13:11:11 -06:00
conf [SPARK-22466][SPARK SUBMIT] export SPARK_CONF_DIR while conf is default 2017-11-09 14:33:08 +09:00
core [SPARK-24920][CORE] Allow sharing Netty's memory pool allocators 2019-01-08 13:11:11 -06:00
data [SPARK-22666][ML][SQL] Spark datasource for image format 2018-09-05 11:59:00 -07:00
dev [SPARK-26554][BUILD][FOLLOWUP] Use GitHub instead of GitBox to check HEADER 2019-01-07 17:54:05 -08:00
docs [SPARK-26448][SQL] retain the difference between 0.0 and -0.0 2019-01-09 13:50:32 -08:00
examples [SPARK-26508][CORE][SQL] Address warning messages in Java reported at lgtm.com 2019-01-01 22:37:28 -06:00
external [SPARK-26541][BUILD] Add -Pdocker-integration-tests to dev/scalastyle 2019-01-05 00:55:17 -08:00
graphx [GRAPHX] Remove unused variables left over by previous refactoring. 2018-11-22 15:43:04 -06:00
hadoop-cloud [SPARK-25956] Make Scala 2.12 as default Scala version in Spark 3.0 2018-11-14 16:22:23 -08:00
launcher [SPARK-26536][BUILD][TEST] Upgrade Mockito to 2.23.4 2019-01-04 19:23:38 -08:00
licenses [SPARK-24654][BUILD] Update, fix LICENSE and NOTICE, and specialize for source vs binary 2018-06-30 19:27:16 -05:00
licenses-binary [SPARK-23654][BUILD] remove jets3t as a dependency of spark 2018-08-16 12:34:23 -07:00
mllib [SPARK-24489][ML] Check for invalid input type of weight data in ml.PowerIterationClustering 2019-01-07 09:15:50 -08:00
mllib-local [SPARK-22450][WIP][CORE][MLLIB][FOLLOWUP] Safely register MultivariateGaussian 2018-11-15 09:22:31 -06:00
project [SPARK-26306][TEST][BUILD] More memory to de-flake SorterSuite 2019-01-04 15:35:23 -06:00
python [SPARK-26549][PYSPARK] Fix for python worker reuse take no effect for parallelize lazy iterable range 2019-01-09 11:55:12 +08:00
R [MINOR][R] Deduplicate RStudio setup documentation 2019-01-02 08:04:36 +08:00
repl [SPARK-26536][BUILD][TEST] Upgrade Mockito to 2.23.4 2019-01-04 19:23:38 -08:00
resource-managers [SPARK-26529] Add debug logs for confArchive when preparing local resource 2019-01-09 10:39:25 +08:00
sbin [SPARK-25891][PYTHON] Upgrade to Py4J 0.10.8.1 2018-10-31 09:55:03 -07:00
sql [SPARK-26448][SQL] retain the difference between 0.0 and -0.0 2019-01-09 13:50:32 -08:00
streaming [SPARK-24522][UI] Create filter to apply HTTP security checks consistently. 2019-01-08 11:25:33 -06:00
tools [SPARK-25956] Make Scala 2.12 as default Scala version in Spark 3.0 2018-11-14 16:22:23 -08:00
.gitattributes [SPARK-3870] EOL character enforcement 2014-10-31 12:39:52 -07:00
.gitignore [MINOR][BUILD] Remove *.crc from .gitignore 2018-11-13 08:34:04 -08:00
appveyor.yml [MINOR][BUILD] Remove -Phive-thriftserver profile within appveyor.yml 2018-07-30 10:01:18 +08:00
CONTRIBUTING.md [SPARK-18073][DOCS][WIP] Migrate wiki to spark.apache.org web site 2016-11-23 11:25:47 +00:00
LICENSE [SPARK-24654][BUILD] Update, fix LICENSE and NOTICE, and specialize for source vs binary 2018-06-30 19:27:16 -05:00
LICENSE-binary [SPARK-23654][BUILD] remove jets3t as a dependency of spark 2018-08-16 12:34:23 -07:00
NOTICE [SPARK-23654][BUILD] remove jets3t as a dependency of spark 2018-08-16 12:34:23 -07:00
NOTICE-binary [SPARK-23654][BUILD] remove jets3t as a dependency of spark 2018-08-16 12:34:23 -07:00
pom.xml [SPARK-26536][BUILD][TEST] Upgrade Mockito to 2.23.4 2019-01-04 19:23:38 -08:00
README.md [DOC] Update some outdated links 2018-09-04 04:39:55 -07:00
scalastyle-config.xml [SPARK-25986][BUILD] Add rules to ban throw Errors in application code 2018-11-14 13:05:18 -08:00

Apache Spark

Spark is a fast and general cluster computing system for Big Data. It provides high-level APIs in Scala, Java, Python, and R, and an optimized engine that supports general computation graphs for data analysis. It also supports a rich set of higher-level tools including Spark SQL for SQL and DataFrames, MLlib for machine learning, GraphX for graph processing, and Spark Streaming for stream processing.

http://spark.apache.org/

Online Documentation

You can find the latest Spark documentation, including a programming guide, on the project web page. This README file only contains basic setup instructions.

Building Spark

Spark is built using Apache Maven. To build Spark and its example programs, run:

build/mvn -DskipTests clean package

(You do not need to do this if you downloaded a pre-built package.)

You can build Spark using more than one thread by using the -T option with Maven, see "Parallel builds in Maven 3". More detailed documentation is available from the project site, at "Building Spark".

For general development tips, including info on developing Spark using an IDE, see "Useful Developer Tools".

Interactive Scala Shell

The easiest way to start using Spark is through the Scala shell:

./bin/spark-shell

Try the following command, which should return 1000:

scala> sc.parallelize(1 to 1000).count()

Interactive Python Shell

Alternatively, if you prefer Python, you can use the Python shell:

./bin/pyspark

And run the following command, which should also return 1000:

>>> sc.parallelize(range(1000)).count()

Example Programs

Spark also comes with several sample programs in the examples directory. To run one of them, use ./bin/run-example <class> [params]. For example:

./bin/run-example SparkPi

will run the Pi example locally.

You can set the MASTER environment variable when running examples to submit examples to a cluster. This can be a mesos:// or spark:// URL, "yarn" to run on YARN, and "local" to run locally with one thread, or "local[N]" to run locally with N threads. You can also use an abbreviated class name if the class is in the examples package. For instance:

MASTER=spark://host:7077 ./bin/run-example SparkPi

Many of the example programs print usage help if no params are given.

Running Tests

Testing first requires building Spark. Once Spark is built, tests can be run using:

./dev/run-tests

Please see the guidance on how to run tests for a module, or individual tests.

There is also a Kubernetes integration test, see resource-managers/kubernetes/integration-tests/README.md

A Note About Hadoop Versions

Spark uses the Hadoop core library to talk to HDFS and other Hadoop-supported storage systems. Because the protocols have changed in different versions of Hadoop, you must build Spark against the same version that your cluster runs.

Please refer to the build documentation at "Specifying the Hadoop Version and Enabling YARN" for detailed guidance on building for a particular distribution of Hadoop, including building for particular Hive and Hive Thriftserver distributions.

Configuration

Please refer to the Configuration Guide in the online documentation for an overview on how to configure Spark.

Contributing

Please review the Contribution to Spark guide for information on how to get started contributing to the project.