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https://issues.apache.org/jira/browse/TAJO-680?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14362917#comment-14362917
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Jihoon Son commented on TAJO-680:
---------------------------------
[~sirpkt], thanks for the good suggestion!
In overall, your suggestion is mostly similar to what I'm doing.
To avoid the code spreading which decreases the readability, I added a new
query rewrite rule to transform the IN subquery statement into the semi-join
statement.
Once the query is transformed, as you said, the remaining part can be processed
with already implemented Tajo's query executors.
Honestly, my work is almost done.
However, since this is a new feature, I'm trying to test various kinds of query
types.
And, fortunately, I found some critical join bugs during tests, and am fixing
those bugs now.
After fixing them, I'll post my patch.
> 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: 0.11.0
>
> 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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