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From "Ashutosh Chauhan (JIRA)" <j...@apache.org>
Subject [jira] [Assigned] (HIVE-19653) Incorrect predicate pushdown for groupby with grouping sets
Date Mon, 28 May 2018 20:26:00 GMT

     [ https://issues.apache.org/jira/browse/HIVE-19653?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Ashutosh Chauhan reassigned HIVE-19653:
---------------------------------------

    Assignee: Zhang Li

> Incorrect predicate pushdown for groupby with grouping sets
> -----------------------------------------------------------
>
>                 Key: HIVE-19653
>                 URL: https://issues.apache.org/jira/browse/HIVE-19653
>             Project: Hive
>          Issue Type: Bug
>          Components: Logical Optimizer
>    Affects Versions: 4.0.0
>            Reporter: Zhang Li
>            Assignee: Zhang Li
>            Priority: Major
>              Labels: pull-request-available
>             Fix For: 4.0.0
>
>         Attachments: HIVE-19653.patch
>
>
> Consider the following query:
> {code:java}
> CREATE TABLE T1(a STRING, b STRING, s BIGINT);
> INSERT OVERWRITE TABLE T1 VALUES ('aaaa', 'bbbb', 123456);
> SELECT * FROM (
> SELECT a, b, sum(s)
> FROM T1
> GROUP BY a, b GROUPING SETS ((), (a), (b), (a, b))
> ) t WHERE a IS NOT NULL;
> {code}
> When hive.optimize.ppd is enabled (and hive.cbo.enable=false), the query will output:
> {code:java}
> NULL	NULL	123456
> NULL	bbbb	123456
> aaaa	NULL	123456
> aaaa	bbbb	123456
> {code}
> We can see the predicate "a IS NOT NULL" takes no effect, which is incorrect.
> When performing PPD optimization for a GBY operator, we should make sure all grouping
sets contains the processing expr before pushdown. otherwise the expr value after GBY is changed
and the result is wrong.



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