Apache Spark - A unified analytics engine for large-scale data processing
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Kazuaki Ishizaki d92cd227cf [SPARK-15985][SQL] Eliminate redundant cast from an array without null or a map without null
## What changes were proposed in this pull request?

This PR eliminates redundant cast from an `ArrayType` with `containsNull = false` or a `MapType` with `containsNull = false`.

For example, in `ArrayType` case, current implementation leaves a cast `cast(value#63 as array<double>).toDoubleArray`. However, we can eliminate `cast(value#63 as array<double>)` if we know `value#63` does not include `null`. This PR apply this elimination for `ArrayType` and `MapType` in `SimplifyCasts` at a plan optimization phase.

In summary, we got 1.2-1.3x performance improvements over the code before applying this PR.
Here are performance results of benchmark programs:
```
  test("Read array in Dataset") {
    import sparkSession.implicits._

    val iters = 5
    val n = 1024 * 1024
    val rows = 15

    val benchmark = new Benchmark("Read primnitive array", n)

    val rand = new Random(511)
    val intDS = sparkSession.sparkContext.parallelize(0 until rows, 1)
      .map(i => Array.tabulate(n)(i => i)).toDS()
    intDS.count() // force to create ds
    val lastElement = n - 1
    val randElement = rand.nextInt(lastElement)

    benchmark.addCase(s"Read int array in Dataset", numIters = iters)(iter => {
      val idx0 = randElement
      val idx1 = lastElement
      intDS.map(a => a(0) + a(idx0) + a(idx1)).collect
    })

    val doubleDS = sparkSession.sparkContext.parallelize(0 until rows, 1)
      .map(i => Array.tabulate(n)(i => i.toDouble)).toDS()
    doubleDS.count() // force to create ds

    benchmark.addCase(s"Read double array in Dataset", numIters = iters)(iter => {
      val idx0 = randElement
      val idx1 = lastElement
      doubleDS.map(a => a(0) + a(idx0) + a(idx1)).collect
    })

    benchmark.run()
  }

Java HotSpot(TM) 64-Bit Server VM 1.8.0_92-b14 on Mac OS X 10.10.4
Intel(R) Core(TM) i5-5257U CPU  2.70GHz

without this PR
Read primnitive array:                   Best/Avg Time(ms)    Rate(M/s)   Per Row(ns)   Relative
------------------------------------------------------------------------------------------------
Read int array in Dataset                      525 /  690          2.0         500.9       1.0X
Read double array in Dataset                   947 / 1209          1.1         902.7       0.6X

with this PR
Read primnitive array:                   Best/Avg Time(ms)    Rate(M/s)   Per Row(ns)   Relative
------------------------------------------------------------------------------------------------
Read int array in Dataset                      400 /  492          2.6         381.5       1.0X
Read double array in Dataset                   788 /  870          1.3         751.4       0.5X
```

An example program that originally caused this performance issue.
```
val ds = Seq(Array(1.0, 2.0, 3.0), Array(4.0, 5.0, 6.0)).toDS()
val ds2 = ds.map(p => {
     var s = 0.0
     for (i <- 0 to 2) { s += p(i) }
     s
   })
ds2.show
ds2.explain(true)
```

Plans before this PR
```
== Parsed Logical Plan ==
'SerializeFromObject [input[0, double, true] AS value#68]
+- 'MapElements <function1>, obj#67: double
   +- 'DeserializeToObject unresolveddeserializer(upcast(getcolumnbyordinal(0, ArrayType(DoubleType,false)), ArrayType(DoubleType,false), - root class: "scala.Array").toDoubleArray), obj#66: [D
      +- LocalRelation [value#63]

== Analyzed Logical Plan ==
value: double
SerializeFromObject [input[0, double, true] AS value#68]
+- MapElements <function1>, obj#67: double
   +- DeserializeToObject cast(value#63 as array<double>).toDoubleArray, obj#66: [D
      +- LocalRelation [value#63]

== Optimized Logical Plan ==
SerializeFromObject [input[0, double, true] AS value#68]
+- MapElements <function1>, obj#67: double
   +- DeserializeToObject cast(value#63 as array<double>).toDoubleArray, obj#66: [D
      +- LocalRelation [value#63]

== Physical Plan ==
*SerializeFromObject [input[0, double, true] AS value#68]
+- *MapElements <function1>, obj#67: double
   +- *DeserializeToObject cast(value#63 as array<double>).toDoubleArray, obj#66: [D
      +- LocalTableScan [value#63]
```

Plans after this PR
```
== Parsed Logical Plan ==
'SerializeFromObject [input[0, double, true] AS value#6]
+- 'MapElements <function1>, obj#5: double
   +- 'DeserializeToObject unresolveddeserializer(upcast(getcolumnbyordinal(0, ArrayType(DoubleType,false)), ArrayType(DoubleType,false), - root class: "scala.Array").toDoubleArray), obj#4: [D
      +- LocalRelation [value#1]

== Analyzed Logical Plan ==
value: double
SerializeFromObject [input[0, double, true] AS value#6]
+- MapElements <function1>, obj#5: double
   +- DeserializeToObject cast(value#1 as array<double>).toDoubleArray, obj#4: [D
      +- LocalRelation [value#1]

== Optimized Logical Plan ==
SerializeFromObject [input[0, double, true] AS value#6]
+- MapElements <function1>, obj#5: double
   +- DeserializeToObject value#1.toDoubleArray, obj#4: [D
      +- LocalRelation [value#1]

== Physical Plan ==
*SerializeFromObject [input[0, double, true] AS value#6]
+- *MapElements <function1>, obj#5: double
   +- *DeserializeToObject value#1.toDoubleArray, obj#4: [D
      +- LocalTableScan [value#1]
```

## How was this patch tested?

Tested by new test cases in `SimplifyCastsSuite`

Author: Kazuaki Ishizaki <ishizaki@jp.ibm.com>

Closes #13704 from kiszk/SPARK-15985.
2016-08-31 12:40:53 +08:00
.github [MINOR][MAINTENANCE] Fix typo for the pull request template. 2016-02-24 00:45:31 -08:00
assembly [SPARK-16967] move mesos to module 2016-08-26 12:25:22 -07:00
bin [SPARK-16781][PYSPARK] java launched by PySpark as gateway may not be the same java used in the spark environment 2016-08-24 20:04:09 +01:00
build [SPARK-14279][BUILD] Pick the spark version from pom 2016-06-06 09:42:50 -07:00
common [SPARK-17314][CORE] Use Netty's DefaultThreadFactory to enable its fast ThreadLocal impl 2016-08-30 13:22:21 -07:00
conf [SPARK-13238][CORE] Add ganglia dmax parameter 2016-08-05 13:07:52 -07:00
core [SPARK-17243][WEB UI] Spark 2.0 History Server won't load with very large application history 2016-08-30 16:33:54 -05:00
data [SPARK-16421][EXAMPLES][ML] Improve ML Example Outputs 2016-08-05 20:57:46 +01:00
dev [SPARK-5682][CORE] Add encrypted shuffle in spark 2016-08-30 09:15:31 -07:00
docs [SPARK-17243][WEB UI] Spark 2.0 History Server won't load with very large application history 2016-08-30 16:33:54 -05:00
examples [SPARK-17001][ML] Enable standardScaler to standardize sparse vectors when withMean=True 2016-08-27 08:48:56 +01:00
external [SPARK-17229][SQL] PostgresDialect shouldn't widen float and short types during reads 2016-08-25 23:22:40 +02:00
graphx [SPARK-16779][TRIVIAL] Avoid using postfix operators where they do not add much and remove whitelisting 2016-08-08 15:54:03 -07:00
launcher [SPARK-13081][PYSPARK][SPARK_SUBMIT] Allow set pythonExec of driver and executor through conf… 2016-08-11 20:08:39 -07:00
licenses [MINOR][BUILD] Add modernizr MIT license; specify "2014 and onwards" in license copyright 2016-06-04 21:41:27 +01:00
mesos [SPARK-16967] move mesos to module 2016-08-26 12:25:22 -07:00
mllib [MINOR][MLLIB][SQL] Clean up unused variables and unused import 2016-08-30 11:24:55 +01:00
mllib-local [ML][MLLIB] The require condition and message doesn't match in SparseMatrix. 2016-08-27 08:46:01 +01:00
project [SPARK-16967] move mesos to module 2016-08-26 12:25:22 -07:00
python [SPARK-17264][SQL] DataStreamWriter should document that it only supports Parquet for now 2016-08-30 11:19:45 +01:00
R [SPARK-16581][SPARKR] Make JVM backend calling functions public 2016-08-29 12:55:32 -07:00
repl [SPARK-17318][TESTS] Fix ReplSuite replicating blocks of object with class defined in repl 2016-08-30 20:04:52 -07:00
sbin [SPARK-16781][PYSPARK] java launched by PySpark as gateway may not be the same java used in the spark environment 2016-08-24 20:04:09 +01:00
sql [SPARK-15985][SQL] Eliminate redundant cast from an array without null or a map without null 2016-08-31 12:40:53 +08:00
streaming [SPARK-17038][STREAMING] fix metrics retrieval source of 'lastReceivedBatch' 2016-08-17 16:31:42 -07:00
tools [SPARK-16535][BUILD] In pom.xml, remove groupId which is redundant definition and inherited from the parent 2016-07-19 11:59:46 +01:00
yarn [SPARK-5682][CORE] Add encrypted shuffle in spark 2016-08-30 09:15:31 -07:00
.gitattributes [SPARK-3870] EOL character enforcement 2014-10-31 12:39:52 -07:00
.gitignore [SPARKR][BUILD] ignore cran-check.out under R folder 2016-08-25 12:11:27 -07:00
.travis.yml [SPARK-16967] move mesos to module 2016-08-26 12:25:22 -07:00
CONTRIBUTING.md [SPARK-6889] [DOCS] CONTRIBUTING.md updates to accompany contribution doc updates 2015-04-21 22:34:31 -07:00
LICENSE [SPARK-16781][PYSPARK] java launched by PySpark as gateway may not be the same java used in the spark environment 2016-08-24 20:04:09 +01:00
NOTICE [MINOR][BUILD] Add modernizr MIT license; specify "2014 and onwards" in license copyright 2016-06-04 21:41:27 +01:00
pom.xml [SPARK-5682][CORE] Add encrypted shuffle in spark 2016-08-30 09:15:31 -07:00
README.md [SPARK-15821][DOCS] Include parallel build info 2016-06-14 13:59:01 +01:00
scalastyle-config.xml [SPARK-16877][BUILD] Add rules for preventing to use Java annotations (Deprecated and Override) 2016-08-04 21:43:05 +01:00

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 and project wiki. 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 developing Spark using an IDE, see Eclipse and IntelliJ.

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.