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https://issues.apache.org/jira/browse/PHOENIX-852?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14104987#comment-14104987
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James Taylor commented on PHOENIX-852:
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In the absence of any hints, I think the default should be to do a skip scan
when possible (i.e. if the leading pk columns are used). If a skip scan is
possible and the RANGE_SCAN_HASH_JOIN hint is present, then do a range scan. If
the SKIP_SCAN_HASH_JOIN is present, then do a skip scan if *some* PK keys are
being joined (doesn't make sense otherwise). This is how the SKIP_SCAN and
RANGE_SCAN hints work now.
> 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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