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https://issues.apache.org/jira/browse/TAJO-680?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14273272#comment-14273272
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Jihoon Son commented on TAJO-680:
---------------------------------
Maybe, it would be better to rewrite the query of the second phase into a
normal join form. In the case of the above example, the query 'select * from
nation where n_regionkey in (results of the first phase)' can be rewritten into
'select * from nation, (results of the first phase) where n_regionkey =
r_regionkey'. Here, in the intermediate results of the first phase, every value
must be unique.
> 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
>
>
> 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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