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https://issues.apache.org/jira/browse/IMPALA-10382?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17245561#comment-17245561
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Shant Hovsepian commented on IMPALA-10382:
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[~xqhe] I assigned this to you if you want to take a pass at it, otherwise I
can't try for the fix.
> Predicate with coalesce on both sides of LOJ isn't NULL filtering
> -----------------------------------------------------------------
>
> Key: IMPALA-10382
> URL: https://issues.apache.org/jira/browse/IMPALA-10382
> Project: IMPALA
> Issue Type: Bug
> Components: Frontend
> Reporter: Shant Hovsepian
> Assignee: Xianqing He
> Priority: Major
>
> A query like the below will have the outer join simplified to an inner join
> when the predicate with coalesce isn't always NULL filtering.
> {code:sql}
> select t1.int_col from alltypestiny t1 left outer join alltypesagg t2 on
> t1.tinyint_col = t2.tinyint_col left outer join alltypes t3 on t1.int_col =
> t3.int_col where t2.tinyint_col >= coalesce(t1.int_col, t2.int_col);
> {code}
> {noformat}
> functional> set ENABLE_OUTER_JOIN_TO_INNER_TRANSFORMATION=true;
> functional> explain select t1.int_col from alltypestiny t1 left outer join
> alltypesagg t2 on t1.tinyint_col = t2.tinyint_col left outer join alltypes t3
> on t1.int_col = t3.int_col where t2.tinyint_col >= coalesce(t1.int_col,
> t2.int_col);
> Query: explain select t1.int_col from alltypestiny t1 left outer join
> alltypesagg t2 on t1.tinyint_col = t2.tinyint_col left outer join alltypes t3
> on t1.int_col = t3.int_col where t2.tinyint_col >= coalesce(t1.int_col,
> t2.int_col)
> +------------------------------------------------------------+
> | Explain String |
> +------------------------------------------------------------+
> | Max Per-Host Resource Reservation: Memory=5.04MB Threads=8 |
> | Per-Host Resource Estimates: Memory=287MB |
> | |
> | PLAN-ROOT SINK |
> | 08:EXCHANGE [UNPARTITIONED] |
> | 04:HASH JOIN [LEFT OUTER JOIN, PARTITIONED] |
> | |--07:EXCHANGE [HASH(t3.int_col)] |
> | | 02:SCAN HDFS [functional.alltypes t3] |
> | 06:EXCHANGE [HASH(t1.int_col)] |
> | 03:HASH JOIN [INNER JOIN, BROADCAST] |
> | |--05:EXCHANGE [BROADCAST] |
> | | 00:SCAN HDFS [functional.alltypestiny t1] |
> | 01:SCAN HDFS [functional.alltypesagg t2] |
> +------------------------------------------------------------+
> Fetched 13 row(s) in 0.02s
> {noformat}
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