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https://issues.apache.org/jira/browse/SPARK-16951?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15412878#comment-15412878
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Nattavut Sutyanyong edited comment on SPARK-16951 at 12/21/16 7:10 PM:
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The semantic of {{NOT IN}} is described in detail in "[Subqueries in Apache
Spark
2.0|https://databricks-prod-cloudfront.cloud.databricks.com/public/4027ec902e239c93eaaa8714f173bcfc/2728434780191932/1483312212640900/6987336228780374/latest.html]";.
Concisely,
"{{x NOT IN (subquery y)}} translates into: {{x <> y1 AND x <> y2 ... AND x <>
yn}}"
When {{x}} and {{subquery y}} cannot produce {{NULL}} value, {{NOT IN}} is
equivalent to its {{NOT EXIST}} counterpart. That is,
{{SELECT .. FROM X WHERE X.C1 NOT IN (SELECT Y.C2 FROM Y)}}
is equivalent to
{{SELECT .. FROM X WHERE NOT EXISTS (SELECT 1 FROM Y WHERE X.C1=Y.C2)}}
however, there are 3 edge cases we need to pay attention to.
Case 1. When {{X.C1}} is {{NULL}}, the row is removed from the result set.
Case 2. When the {{subquery Y}} can produce {{NULL}} value to the output column
{{Y.C2}}, the result is an empty set.
-Case 3. When the {{subquery Y}} produce an empty set, SQL language defines
that the subquery will return a row of {{NULL}} value, hence this is like case
2 which returns an empty set.-
was (Author: nsyca):
The semantic of {{NOT IN}} is described in detail in "[Subqueries in Apache
Spark
2.0|https://databricks-prod-cloudfront.cloud.databricks.com/public/4027ec902e239c93eaaa8714f173bcfc/2728434780191932/1483312212640900/6987336228780374/latest.html]";.
Concisely,
"{{x NOT IN (subquery y)}} translates into: {{x <> y1 AND x <> y2 ... AND x <>
yn}}"
When {{x}} and {{subquery y}} cannot produce {{NULL}} value, {{NOT IN}} is
equivalent to its {{NOT EXIST}} counterpart. That is,
{{SELECT .. FROM X WHERE X.C1 NOT IN (SELECT Y.C2 FROM Y)}}
is equivalent to
{{SELECT .. FROM X WHERE NOT EXISTS (SELECT 1 FROM Y WHERE X.C1=Y.C2)}}
however, there are 3 edge cases we need to pay attention to.
Case 1. When {{X.C1}} is {{NULL}}, the row is removed from the result set.
Case 2. When the {{subquery Y}} can produce {{NULL}} value to the output column
{{Y.C2}}, the result is an empty set.
Case 3. When the {{subquery Y}} produce an empty set, SQL language defines that
the subquery will return a row of {{NULL}} value, hence this is like case 2
which returns an empty set.
> Alternative implementation of NOT IN to Anti-join
> -------------------------------------------------
>
> Key: SPARK-16951
> URL: https://issues.apache.org/jira/browse/SPARK-16951
> Project: Spark
> Issue Type: Sub-task
> 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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