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From "Nattavut Sutyanyong (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (SPARK-18597) Do not push down filters for LEFT ANTI JOIN
Date Mon, 28 Nov 2016 16:48:58 GMT

    [ https://issues.apache.org/jira/browse/SPARK-18597?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15702454#comment-15702454
] 

Nattavut Sutyanyong commented on SPARK-18597:
---------------------------------------------

[~hvanhovell], @dongjoon, [~smilegator] FYI:

I edited the description to reflect the correct behaviour of the {{LeftAnti}} in the example.
The correct answer is all the rows from tbl_a as there is no row in tbl_a that satisfies the
predicate tbl_a.c1 = tbl_a.c2 in the ON clause. By the LeftAnti semantics of tbl_a except
rows that satisfy the predicate in the ON clause, all rows from tbl_a are returned. 

> Do not push down filters for LEFT ANTI JOIN
> -------------------------------------------
>
>                 Key: SPARK-18597
>                 URL: https://issues.apache.org/jira/browse/SPARK-18597
>             Project: Spark
>          Issue Type: Bug
>          Components: SQL
>            Reporter: Herman van Hovell
>            Assignee: Herman van Hovell
>            Priority: Minor
>              Labels: correctness
>             Fix For: 2.1.0
>
>
> The optimizer pushes down filters for left anti joins. This unfortunately has the opposite
effect. For example:
> {noformat}
> sql("create or replace temporary view tbl_a as values (1, 5), (2, 1), (3, 6) as t(c1,
c2)")
> sql("create or replace temporary view tbl_b as values 1 as t(c1)")
> sql("""
> select *
> from   tbl_a
>        left anti join tbl_b on ((tbl_a.c1 = tbl_a.c2) is null or tbl_a.c1 = tbl_a.c2)
> """)
> {noformat}
> Should return rows [2, 1] & [3, 6], but returns no rows.
> The upside is that this will only happen when you use a really weird anti-join (only
referencing the table on the left hand side).



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