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From "Gabriel Reid (JIRA)" <j...@apache.org>
Subject [jira] [Created] (CRUNCH-72) Cartesian#cross loads all data in memory per parallel mapper
Date Thu, 20 Sep 2012 19:02:07 GMT
Gabriel Reid created CRUNCH-72:
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             Summary: Cartesian#cross loads all data in memory per parallel mapper
                 Key: CRUNCH-72
                 URL: https://issues.apache.org/jira/browse/CRUNCH-72
             Project: Crunch
          Issue Type: Bug
            Reporter: Gabriel Reid
            Assignee: Gabriel Reid


Cartesian#cross currently uses the PTable#cogroup method to join two sets of data together;
this results in all data from both sides of the join being loaded in memory at one time. This
can be a real problem with cartesian joins because of the quantity of data being joined.

Using PTable#join instead of PTable#cogroup will reduce the memory usage by 50%, which can
be the difference between a cartesian join working or failing with an OOME.

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