[jira] [Commented] (DRILL-979) Wrong result for Union-All query

["Aman Sinha (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/DRILL-979?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14060265#comment-14060265 ] 

Aman Sinha commented on DRILL-979:
----------------------------------

Uploaded a patch for this issue.   For Union (and other set operations) the column names and ordering is already decided by the left child so we should not have to add a Project above the Union to do the final reordering which can potentially have side-effects.   As part of this, I have added a method needsFinalReordering() to the Prel interface that is implemented by various Prels.

> Wrong result for Union-All query
> --------------------------------
>
>                 Key: DRILL-979
>                 URL: https://issues.apache.org/jira/browse/DRILL-979
>             Project: Apache Drill
>          Issue Type: Bug
>          Components: Execution - Operators
>            Reporter: Aman Sinha
>            Assignee: Aman Sinha
>         Attachments: 0001-DRILL-979-For-Union-All-don-t-do-final-column-re-ord.patch
>
>
> The following query gives wrong results.   The last 5 rows should be non-null values from region table but they are nulls in the result set. 
> 0: jdbc:drill:zk=local> select n_nationkey, n_nationkey from nation union all select r_regionkey, r_regionkey from region;
> +-------------+--------------+
> | n_nationkey | n_nationkey0 |
> +-------------+--------------+
> | 0           | 0            |
> | 1           | 1            |
> | 2           | 2            |
> | 3           | 3            |
> | 4           | 4            |
> | 5           | 5            |
> | 6           | 6            |
> | 7           | 7            |
> | 8           | 8            |
> | 9           | 9            |
> | 10          | 10           |
> | 11          | 11           |
> | 12          | 12           |
> | 13          | 13           |
> | 14          | 14           |
> | 15          | 15           |
> | 16          | 16           |
> | 17          | 17           |
> | 18          | 18           |
> | 19          | 19           |
> | 20          | 20           |
> | 21          | 21           |
> | 22          | 22           |
> | 23          | 23           |
> | 24          | 24           |
> | null        | null         |
> | null        | null         |
> | null        | null         |
> | null        | null         |
> | null        | null         |
> +-------------+--------------+
> 30 rows selected (0.166 seconds)



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