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From "Josh Wills (JIRA)" <>
Subject [jira] [Commented] (CRUNCH-278) Improvements to MapsideJoin code
Date Fri, 11 Oct 2013 15:02:42 GMT


Josh Wills commented on CRUNCH-278:

I don't think it would prevent using the library functions-- it would just look like:

PCollection<K> stuff = ...;
PTable<K, V> cnt = stuff.count();
ReadableSourceBundle<Pair<K, V>> = cnt.toBundle();

i.e., you would just do whatever transforms you wanted to apply before converting the PCollection
to a bundle.

That said, I think that if we had an instance like this, we would be inclined to kick off
an MR job vs. just reading the data in memory and doing the count/aggregation ourselves using
the in-memory pipeline. Maybe an option on the API to control that?

> Improvements to MapsideJoin code
> --------------------------------
>                 Key: CRUNCH-278
>                 URL:
>             Project: Crunch
>          Issue Type: Bug
>          Components: Core, MapReduce Patterns
>            Reporter: Josh Wills
>            Assignee: Josh Wills
>         Attachments: CRUNCH-278.patch
> The fact that we have special-case code in the MapsideJoinStrategy for the in-memory
and MR-based Pipeline instances has always bugged me, so I set out to eliminate the distinction
between the two impls by creating a new interface, ReadableSourceBundle<T>, that encapsulates
the MR and in-memory specific logic for doing mapside joins in order to remove the special-case
code in MapsideJoinStrategy and hopefully make other implementations that use our mapside-join
patterns much easier to test.

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