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https://issues.apache.org/jira/browse/SPARK-16951?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15413773#comment-15413773
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Nattavut Sutyanyong commented on SPARK-16951:
---------------------------------------------
I found this
[document|https://asktom.oracle.com/pls/apex/f?p=100:11:0::NO::P11_QUESTION_ID:442029737684]
is the closest I can find discussing this very fine point in the reply to a
question at October 02, 2002 - 10:25 am UTC
{noformat}
Because NULL means -- gee, I don't know. (litterally, null means Unknown)
So, the predicate
where x not in ( NULL )
evaluates to neither TRUE, nor FALSE
ops$tk...@ora817dev.us.oracle.com> select * from dual where dummy not in ( NULL
);
no rows selected
{noformat}
> Alternative implementation of NOT IN to Anti-join
> -------------------------------------------------
>
> Key: SPARK-16951
> URL: https://issues.apache.org/jira/browse/SPARK-16951
> Project: Spark
> Issue Type: Improvement
> Components: SQL
> Affects Versions: 2.0.0
> Reporter: Nattavut Sutyanyong
>
> A transformation currently used to process {{NOT IN}} subquery is to rewrite
> to a form of Anti-join with null-aware property in the Logical Plan and then
> translate to a form of {{OR}} predicate joining the parent side and the
> subquery side of the {{NOT IN}}. As a result, the presence of {{OR}}
> predicate is limited to the nested-loop join execution plan, which will have
> a major performance implication if both sides' results are large.
> This JIRA sketches an idea of changing the OR predicate to a form similar to
> the technique used in the implementation of the Existence join that addresses
> the problem of {{EXISTS (..) OR ..}} type of queries.
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