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From "Maryann Xue (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (PHOENIX-1556) Base hash versus sort merge join decision on cost
Date Wed, 14 Mar 2018 04:43:00 GMT

    [ https://issues.apache.org/jira/browse/PHOENIX-1556?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16398099#comment-16398099
] 

Maryann Xue commented on PHOENIX-1556:
--------------------------------------

Done. All 5.x and 4.x branches have been synced with my latest commits.

> Base hash versus sort merge join decision on cost
> -------------------------------------------------
>
>                 Key: PHOENIX-1556
>                 URL: https://issues.apache.org/jira/browse/PHOENIX-1556
>             Project: Phoenix
>          Issue Type: Sub-task
>            Reporter: James Taylor
>            Assignee: Maryann Xue
>            Priority: Major
>              Labels: CostBasedOptimization
>             Fix For: 4.14.0, 5.0.0
>
>         Attachments: PHOENIX-1556.patch
>
>
> At compile time, we know how many guideposts (i.e. how many bytes) will be scanned for
the RHS table. We should, by default, base the decision of using the hash-join verus many-to-many
join on this information.
> Another criteria (as we've seen in PHOENIX-4508) is whether or not the tables being
joined are already ordered by the join key. In that case, it's better to always use the sort
merge join.



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