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https://issues.apache.org/jira/browse/PHOENIX-852?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14099331#comment-14099331
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Maryann Xue commented on PHOENIX-852:
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[~jamestaylor] Just realized one thing: Some child-to-parent joins will cover a
full range of PKs, for example, an employee basic info table joining a an
employee payroll table on employee_id. Thus, this optimization would be an
extra overhead. So I'd like to add a switch and I'm thinking of two options:
1. hint
2. a limit on the size of the value set, say, if too many point look-ups, we
simply do a full scan.
What do you think? either of them or both? if (2), what default limit value
would be reasonable?
> Optimize child/parent foreign key joins
> ---------------------------------------
>
> Key: PHOENIX-852
> URL: https://issues.apache.org/jira/browse/PHOENIX-852
> Project: Phoenix
> Issue Type: Improvement
> Reporter: James Taylor
> Assignee: Maryann Xue
>
> Often times a join will occur from a child to a parent. Our current algorithm
> would do a full scan of one side or the other. We can do much better than
> that if the HashCache contains the PK (or even part of the PK) from the table
> being joined to. In these cases, we should drive the second scan through a
> skip scan on the server side.
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