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From "Gopal V (JIRA)" <>
Subject [jira] [Updated] (HIVE-7158) Use Tez auto-parallelism in Hive
Date Tue, 10 Jun 2014 17:17:03 GMT


Gopal V updated HIVE-7158:

    Attachment: HIVE-7158.5.patch

Incorporated [~leftylev]'s comments from RB & added punctuation for

"When enabled Hive will" to "When enabled, Hive will".

> Use Tez auto-parallelism in Hive
> --------------------------------
>                 Key: HIVE-7158
>                 URL:
>             Project: Hive
>          Issue Type: Bug
>            Reporter: Gunther Hagleitner
>            Assignee: Gunther Hagleitner
>         Attachments: HIVE-7158.1.patch, HIVE-7158.2.patch, HIVE-7158.3.patch, HIVE-7158.4.patch,
> Tez can optionally sample data from a fraction of the tasks of a vertex and use that
information to choose the number of downstream tasks for any given scatter gather edge.
> Hive estimates the count of reducers by looking at stats and estimates for each operator
in the operator pipeline leading up to the reducer. However, if this estimate turns out to
be too large, Tez can reign in the resources used to compute the reducer.
> It does so by combining partitions of the upstream vertex. It cannot, however, add reducers
at this stage.
> I'm proposing to let users specify whether they want to use auto-parallelism or not.
If they do there will be scaling factors to determine max and min reducers Tez can choose
from. We will then partition by max reducers, letting Tez sample and reign in the count up
until the specified min.

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