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New Features

  • Support for Sequence files as well as better support in general for adding other I/O types. Essentially, if you have an InputFormat or OutputFormat, you can plug them into a DataSource or DataSink, respectively, and you're good to go. Take a look at how I/O for text files and sequence files are implemented to get the idea.

  • The ability to create a DList given a sequence of elements. There is now an apply method for DLists and take a look at the tabulate method. Also added is pimping of regular collections into DLists using toDList. See DList docs

  • A method to write out delimited text files - TextOutput.toDelimitedTextFile. Thanks to Alex Cozi for this one.

  • Better logging. Scoobi now logs input and output paths, how many map-reduce steps will be executed, which step is being executed, map/reduce task progress, number of reducers for the current step, map- reduce job ids, etc. Turning off standard Hadoop logging in is useful.

  • A new way to "persist". There's a new class, 'Job', which allows you to build up a list of the DLists and DObjects (more on those below) you want included as part of the computation. Here's how you use it:

    val job = Job() job << toTextFile(a, "hdfs://...") job << toSequenceFile(b, "hdfs://...")

This doesn't replace persist but allows you to effectivly "sprinkle" the persisting throughout your code. Note that the call to run() triggers the map-reduce job(s) and on completion will clear out the list of DLists that were persisted. That means you can reuse a Job object.

  • A new DList method materialize, that turns a DList[A] into a DObject[Iterable[A]]. A DObject is really just a wrapper (there are other plans for it in the future) and you get to the value inside using its get method. materialize makes it possible to implement iterative algorithms that converge.

Here's how you use it:

val a: DList[Int] = ...
val x: DObject[Iterable[Int]] = a.materialize

val job = Job()
job << use(x)  // note: in later versions of scoobi, this becomes 'job << x.use'

x.get foreach { println }
  • A bunch of performance improvements relating mostly to reducers and partitioners.

  • A distinct method on DLists.

  • Replacing the Ordering type class constraint on 'groupByKey' with a new type class constraint, Grouping. Grouping is more detailed and is a complete abstraction of all parts of Hadoop's sort-and-shuffle phase: partitioning, value grouping, and key sorting. Implicit values are provided for types with 'Ordering' and types that are 'Comparable'. You can write your own for implementing functionality such as secondary-sorting.

  • Simple left and right outer joins for two DLists, with an illustrative example

  • Support glob patterns in input path specification.

Bug Fixes

  • Handle MSCRs with a flatten node, but no group by key
  • Fix bug for when outputs are added to CopyTable.
  • Make finding related nodes less greedy
  • Fix bug in generation of identity reducers
  • JarBuilder modified to enable running from eclipse
  • Fix an issue where Scoobi would die on writing long strings

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