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Latest commit b1bb9e9 @johnynek johnynek Merge pull request #1507 from richwhitjr/develop
Utility methods for running Executions in parallel
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logo Add scalding logo
maple/src/main/java/com remove unused imports from maple java code
project Use `wartremover` to guard against careless use of `_.get`
scalding-args/src Override hashCode for Args
scalding-avro Move Scalding to 2.10/2.11
scalding-benchmarks/src/test/scala/com/twitter/scalding import hygiene: remove unused imports
scalding-commons Use string interpolation in `Checkpoint.scala`
scalding-core Merge pull request #1507 from richwhitjr/develop
scalding-date/src Add implicit Ordering[RichDate]
scalding-db Use `wartremover` to guard against careless use of `_.get`
scalding-hadoop-test/src Limit task history fields consumed from hraven
scalding-hraven refactor toFlowStepHistory
scalding-jdbc/src Fixes
scalding-json/src import hygiene: remove unused imports
scalding-parquet-fixtures/src/test/resources Copy over code from parquet-cascading, drop dep
scalding-parquet-scrooge-fixtures/src/test/resources Move the scrooge fixtures into their own build targets so the local b…
scalding-parquet-scrooge Fix pig exclude, unused imports, parquet-scrooge test
scalding-parquet Warning from the parquet-cascading merge in
scalding-repl Use `wartremover` to guard against careless use of `_.get`
scalding-serialization/src Use `wartremover` to guard against careless use of `_.get`
scalding-thrift-macros-fixtures/src/test/resources Move the scrooge fixtures into their own build targets so the local b…
scalding-thrift-macros Use `wartremover` to guard against careless use of `_.get`
scripts Fix references to Build.scala in other places
tutorial Change ScaldingILoop
.gitignore Update the build
.travis.blacklist Add scalding-parquet-fixtures to travis blacklist
.travis.yml Update Scala version to 2.10.6 bumping version to 0.15.0; algebird to 0.10.1 Add
LICENSE Initial Import
NOTICE Initial Import Update
build.sbt Fix `wartremover` to only run during the `compile` phase
sbt Update Scala version to 2.10.6
version.sbt Setting version to 0.16.1-SNAPSHOT


Scalding is a Scala library that makes it easy to specify Hadoop MapReduce jobs. Scalding is built on top of Cascading, a Java library that abstracts away low-level Hadoop details. Scalding is comparable to Pig, but offers tight integration with Scala, bringing advantages of Scala to your MapReduce jobs.

Scalding Logo

Current version: 0.15.0

Word Count

Hadoop is a distributed system for counting words. Here is how it's done in Scalding.

package com.twitter.scalding.examples

import com.twitter.scalding._

class WordCountJob(args: Args) extends Job(args) {
    .flatMap { line => tokenize(line) }
    .groupBy { word => word } // use each word for a key
    .size // in each group, get the size
    .write(TypedTsv[(String, Long)](args("output")))

  // Split a piece of text into individual words.
  def tokenize(text: String): Array[String] = {
    // Lowercase each word and remove punctuation.
    text.toLowerCase.replaceAll("[^a-zA-Z0-9\\s]", "").split("\\s+")

Notice that the tokenize function, which is standard Scala, integrates naturally with the rest of the MapReduce job. This is a very powerful feature of Scalding. (Compare it to the use of UDFs in Pig.)

You can find more example code under examples/. If you're interested in comparing Scalding to other languages, see our Rosetta Code page, which has several MapReduce tasks in Scalding and other frameworks (e.g., Pig and Hadoop Streaming).

Documentation and Getting Started

Please feel free to use the beautiful Scalding logo artwork anywhere.

Code of Conduct

This, and all projects, are under the Twitter Open Source Code of Conduct. Additionally, see the Typelevel Code of Conduct for specific examples of harassing behavior that are not tolerated.


There is a script (called sbt) in the root that loads the correct sbt version to build:

  1. ./sbt update (takes 2 minutes or more)
  2. ./sbt test
  3. ./sbt assembly (needed to make the jar used by the scald.rb script)

The test suite takes a while to run. When you're in sbt, here's a shortcut to run just one test:

> test-only com.twitter.scalding.FileSourceTest

Please refer to FAQ page if you encounter problems when using sbt.

We use Travis CI to verify the build: Build Status

We use Coveralls for code coverage results: Coverage Status

Scalding modules are available from maven central.

The current groupid and version for all modules is, respectively, "com.twitter" and 0.16.0-RC1.

Current published artifacts are

  • scalding-core_2.10
  • scalding-args_2.10
  • scalding-date_2.10
  • scalding-commons_2.10
  • scalding-avro_2.10
  • scalding-parquet_2.10
  • scalding-repl_2.10

The suffix denotes the scala version.


  • Ebay
  • Etsy
  • Sharethrough
  • Snowplow Analytics
  • Soundcloud
  • Twitter

To see a full list of users or to add yourself, see the wiki


For user questions or scalding development (internals, extending, release planning):!forum/scalding-dev (Google search also works as a first step)

In the remote possibility that there exist bugs in this code, please report them to:

Follow @Scalding on Twitter for updates.

Chat: Gitter


Thanks for assistance and contributions:

A full list of contributors can be found on GitHub.


Copyright 2013 Twitter, Inc.

Licensed under the Apache License, Version 2.0:

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