[jira] [Comment Edited] (HIVE-13069) Enable cartesian product merging

["Ashutosh Chauhan (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HIVE-13069?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15171147#comment-15171147 ] 

Ashutosh Chauhan edited comment on HIVE-13069 at 2/28/16 7:36 PM:
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Why leftAlias is null for join tree without any join condition ?

I wonder better fix might be to ensure leftAlias is not null under such conditions.


was (Author: ashutoshc):
Why leftAlias is null for join tree without any join condition ?

> Enable cartesian product merging
> --------------------------------
>
>                 Key: HIVE-13069
>                 URL: https://issues.apache.org/jira/browse/HIVE-13069
>             Project: Hive
>          Issue Type: Improvement
>          Components: Parser
>            Reporter: Jesus Camacho Rodriguez
>            Assignee: Jesus Camacho Rodriguez
>         Attachments: HIVE-13069.patch
>
>
> Currently we can merge 2-way joins into n-way joins when the joins are executed over the same column.
> In turn, CBO might produce plans containing cartesian products if the join columns are constant values; after HIVE-12543 went in, this is rather common, as those constant columns are correctly pruned. However, currently we do not merge a cartesian product with two inputs into a cartesian product with multiple inputs, which could result in performance loss.



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