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https://issues.apache.org/jira/browse/PHOENIX-852?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14088735#comment-14088735
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James Taylor commented on PHOENIX-852:
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I think it'd be easiest to just take the row key columns from the results of
the smaller table, and use them to generate a query with an IN clause. You can
use our row value constructor syntax for this. See
RowValueConstructorIT.testQueryMoreWithInListRowValueConstructor() for an
example. You wouldn't even send a hash cache to the region servers. Just let
the IN query go through the normal path, as it's executed pretty optimally
already. I think you'd need to generate a different query plan altogether for
this, though.
> 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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