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https://issues.apache.org/jira/browse/CRUNCH-57?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Kiyan Ahmadizadeh updated CRUNCH-57:
------------------------------------

    Attachment: CRUNCH-57.patch

This patch gives an implementation.  A static length() method is added to 
Aggregate.java and used from PCollectionImpl and MemCollection to implement a 
length() function defined in the PCollection interface.  The implementation for 
Aggregate#length closely follows the implementation of Aggregate#count with a 
few tweaks.

This functionality is exposed in Scala by adding a length function to trait 
PCollectionLike. 

Integration tests are added for this functionality. 
                
> Add a length function to PCollection
> ------------------------------------
>
>                 Key: CRUNCH-57
>                 URL: https://issues.apache.org/jira/browse/CRUNCH-57
>             Project: Crunch
>          Issue Type: New Feature
>          Components: Core
>    Affects Versions: 0.3.0
>            Reporter: Kiyan Ahmadizadeh
>            Assignee: Josh Wills
>         Attachments: CRUNCH-57.patch
>
>
> Sometimes it's useful and interesting to compute the number of elements in a 
> PCollection.
>  
> For example, suppose there was an initial PCollection that was then filtered 
> into another.  If I'm interested in how many elements of the original 
> PCollection matched the filter, I'll have to write extra code to compute this.
> PCollections should have a length method that, when called, computes the 
> number of elements in the PCollection and returns the result. 

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