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From "Josh Wills (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (CRUNCH-88) Multiple parallelDos on a PGroupedTableImpl does not work
Date Fri, 05 Oct 2012 18:58:02 GMT

     [ https://issues.apache.org/jira/browse/CRUNCH-88?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Josh Wills updated CRUNCH-88:
-----------------------------

    Attachment: CRUNCH-88.patch

So it turned out to be an execution problem, not a planning problem. If a groupByKey has multiple
children, the first child can consume the output of all of the Iterable<V> values before
the other children get a chance to process them. The solution I implemented detects when we're
in this situation and caches the Iterable<V> in memory so it can be processed by each
child in turn. I imagine we'll need to make it more clever over time (to support, e.g., spilling
to disk), but this fixes the immediate problem.
                
> Multiple parallelDos on a PGroupedTableImpl does not work
> ---------------------------------------------------------
>
>                 Key: CRUNCH-88
>                 URL: https://issues.apache.org/jira/browse/CRUNCH-88
>             Project: Crunch
>          Issue Type: Bug
>    Affects Versions: 0.3.0
>            Reporter: Gabriel Reid
>            Assignee: Gabriel Reid
>         Attachments: CRUNCH-88.patch, CRUNCH-88.patch
>
>
> Creating multiple distinct PCollections based on a single PGroupedTableImpl does not
work correctly - the content of the PGroupedTableImpl will only be sent to a single outgoing
PCollection, and all other PCollections that stem from the grouped table will not receive
any data.

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