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From "Gabriel Reid (JIRA)" <>
Subject [jira] [Updated] (CRUNCH-216) Transpose arguments in MapsideJoinStrategy.join
Date Sun, 16 Feb 2014 06:05:19 GMT


Gabriel Reid updated CRUNCH-216:

    Attachment: CRUNCH-216b.patch

About reversing both left and right outer joins, only one outer join type is supported (left-outer
for the legacy mapside join, and right-outer for the transposed version). This is because
there are multiple replicas of the in-memory side of the join, so it's not currently possible
to emit a single copy of each unmatched value from the in-memory side of the join.

I've made the only reversing of the right-outer join on the transposed version more explicit
in this patch, and removed the factory methods for legacy instances of MapsideJoinStrategy.

> Transpose arguments in MapsideJoinStrategy.join
> -----------------------------------------------
>                 Key: CRUNCH-216
>                 URL:
>             Project: Crunch
>          Issue Type: Improvement
>            Reporter: Gabriel Reid
>         Attachments: CRUNCH-216.patch, CRUNCH-216b.patch
> The MapsideJoinStrategy currently specifies that the smaller table in the join (i.e.
the table to be replicated and loaded in memory) should be on the right-hand side of the join.
> This is the opposite of what is done in all other join strategies, making it impossible
to just switch out another join strategy for a MapsideJoinStrategy. The MapsideJoinStrategy
could be brought in line with the other JoinStrategies to expect the smaller of two tables
to be provided as the left-side table.

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