Apache Spark - A unified analytics engine for large-scale data processing
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Wenchen Fan de6ad3dfa7 [SPARK-19309][SQL] disable common subexpression elimination for conditional expressions
## What changes were proposed in this pull request?

As I pointed out in https://github.com/apache/spark/pull/15807#issuecomment-259143655 , the current subexpression elimination framework has a problem, it always evaluates all common subexpressions at the beginning, even they are inside conditional expressions and may not be accessed.

Ideally we should implement it like scala lazy val, so we only evaluate it when it gets accessed at lease once. https://github.com/apache/spark/issues/15837 tries this approach, but it seems too complicated and may introduce performance regression.

This PR simply stops common subexpression elimination for conditional expressions, with some cleanup.

## How was this patch tested?

regression test

Author: Wenchen Fan <wenchen@databricks.com>

Closes #16659 from cloud-fan/codegen.
2017-01-23 13:31:26 +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-18695] Bump master branch version to 2.2.0-SNAPSHOT 2016-12-02 21:09:37 -08:00
bin [SPARK-1267][SPARK-18129] Allow PySpark to be pip installed 2016-11-16 14:22:15 -08:00
build [SPARK-18638][BUILD] Upgrade sbt, Zinc, and Maven plugins 2016-12-03 10:36:19 +00:00
common [SPARK-19178][SQL] convert string of large numbers to int should return null 2017-01-12 22:52:34 -08:00
conf [SPARK-11653][DEPLOY] Allow spark-daemon.sh to run in the foreground 2016-10-20 09:49:58 +01:00
core [SPARK-19117][SPARK-18922][TESTS] Fix the rest of flaky, newly introduced and missed test failures on Windows 2017-01-21 14:08:01 +00:00
data [SPARK-16421][EXAMPLES][ML] Improve ML Example Outputs 2016-08-05 20:57:46 +01:00
dev [SPARK-16654][CORE] Add UI coverage for Application Level Blacklisting 2017-01-19 09:08:18 -06:00
docs [SPARK-19302][DOC][MINOR] Fix the wrong item format in security.md 2017-01-20 14:15:18 +00:00
examples [SPARK-19227][SPARK-19251] remove unused imports and outdated comments 2017-01-18 09:44:32 +00:00
external [SPARK-14536][SQL] fix to handle null value in array type column for postgres. 2017-01-20 19:23:20 -08:00
graphx [SPARK-3249][DOC] Fix links in ScalaDoc that cause warning messages in sbt/sbt unidoc 2017-01-17 12:28:15 +00:00
launcher [SPARK-19227][SPARK-19251] remove unused imports and outdated comments 2017-01-18 09:44:32 +00:00
licenses [MINOR][BUILD] Add modernizr MIT license; specify "2014 and onwards" in license copyright 2016-06-04 21:41:27 +01:00
mllib [SPARK-19291][SPARKR][ML] spark.gaussianMixture supports output log-likelihood. 2017-01-21 21:26:14 -08:00
mllib-local [SPARK-17807][CORE] split test-tags into test-JAR 2016-12-21 16:37:20 -08:00
project [SPARK-19069][CORE] Expose task 'status' and 'duration' in spark history server REST API. 2017-01-20 10:49:05 -06:00
python [SPARK-19229][SQL] Disallow Creating Hive Source Tables when Hive Support is Not Enabled 2017-01-22 20:37:37 -08:00
R [SPARK-19291][SPARKR][ML] spark.gaussianMixture supports output log-likelihood. 2017-01-21 21:26:14 -08:00
repl [SPARK-19227][SPARK-19251] remove unused imports and outdated comments 2017-01-18 09:44:32 +00:00
resource-managers [SPARK-19227][SPARK-19251] remove unused imports and outdated comments 2017-01-18 09:44:32 +00:00
sbin [SPARK-19083] sbin/start-history-server.sh script use of $@ without quotes 2017-01-06 09:57:49 -08:00
sql [SPARK-19309][SQL] disable common subexpression elimination for conditional expressions 2017-01-23 13:31:26 +08:00
streaming [SPARK-19182][DSTREAM] Optimize the lock in StreamingJobProgressListener to not block UI when generating Streaming jobs 2017-01-18 10:55:31 -08:00
tools [SPARK-18695] Bump master branch version to 2.2.0-SNAPSHOT 2016-12-02 21:09:37 -08:00
.gitattributes [SPARK-3870] EOL character enforcement 2014-10-31 12:39:52 -07:00
.gitignore [SPARK-1267][SPARK-18129] Allow PySpark to be pip installed 2016-11-16 14:22:15 -08:00
.travis.yml [SPARK-16967] move mesos to module 2016-08-26 12:25:22 -07:00
appveyor.yml [SPARK-17200][PROJECT INFRA][BUILD][SPARKR] Automate building and testing on Windows (currently SparkR only) 2016-09-08 08:26:59 -07:00
CONTRIBUTING.md [SPARK-18073][DOCS][WIP] Migrate wiki to spark.apache.org web site 2016-11-23 11:25:47 +00:00
LICENSE [SPARK-17960][PYSPARK][UPGRADE TO PY4J 0.10.4] 2016-10-21 09:48:24 +01:00
NOTICE [SPARK-18262][BUILD][SQL] JSON.org license is now CatX 2016-11-10 10:20:03 -08:00
pom.xml [SPARK-18782][BUILD] Bump Hadoop 2.6 version to use Hadoop 2.6.5 2017-01-18 09:46:34 +00:00
README.md [MINOR][DOCS] Remove Apache Spark Wiki address 2016-12-10 16:40:10 +00:00
scalastyle-config.xml [SPARK-13747][CORE] Fix potential ThreadLocal leaks in RPC when using ForkJoinPool 2016-12-13 09:53:22 -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.

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" 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.