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https://issues.apache.org/jira/browse/PHOENIX-1556?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16369777#comment-16369777
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Maryann Xue commented on PHOENIX-1556:
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Thank you, [~rajeshbabu], for reminding me! 5.x branch has now caught up with
all my recent check-ins.
> 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
>
> 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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