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https://issues.apache.org/jira/browse/TAJO-680?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14274788#comment-14274788
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Hyunsik Choi commented on TAJO-680:
-----------------------------------
RowConstantFromDiskEval may play the same role of MergeScanner which reads the
shuffled intermediate result. I think that this work may requires only new
representation layer for IN subquery. Then, we can reuse existing physical
operators. Uncorrelated IN subquery is equivalent to hash shuffle and semi join.
> Improve the IN operator to support sub queries
> ----------------------------------------------
>
> Key: TAJO-680
> URL: https://issues.apache.org/jira/browse/TAJO-680
> Project: Tajo
> Issue Type: Improvement
> Components: distributed query plan, parser
> Reporter: Jihoon Son
> Assignee: Jihoon Son
> Fix For: 0.11
>
> Attachments: Distributed plan.png, Logical plan.png
>
>
> Currently, the IN operator can be used with only sets of values.
> We need to improve it to support sub queries as the following example query.
> {noformat}
> tajo> select * from nation where n_regionkey in (select r_regionkey from
> region);
> {noformat}
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