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https://issues.apache.org/jira/browse/PHOENIX-852?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14105475#comment-14105475
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Maryann Xue commented on PHOENIX-852:
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Suppose the child table has PK c1,c2,c3, and the parent has PK c1,c2, and the
(c1,c2) values from the child table fully occupies the key space of (c1,c2) in
the parent table, and c3 is about 10-20 different values to each identical
(c1,c2), how much impact would there be on performance if we do skip scan for
this case?
> 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
> Attachments: 852.patch, PHOENIX-852.patch
>
>
> 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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