[jira] [Comment Edited] (DERBY-4327) Implement optimizer support for bushy trees.

["Dag H. Wanvik (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/DERBY-4327?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13758991#comment-13758991 ] 

Dag H. Wanvik edited comment on DERBY-4327 at 9/5/13 11:28 AM:
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Some links:

https://www.simple-talk.com/sql/performance/join-reordering-and-bushy-plans/

http://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CDwQFjAA&url=http%3A%2F%2Fciteseerx.ist.psu.edu%2Fviewdoc%2Fdownload%3Fdoi%3D10.1.1.56.6379%26rep%3Drep1%26type%3Dpdf&ei=3GUoUtbTN8uQ0QWh0oDYAw&usg=AFQjCNFme8BiQI59ZnxP68M6cnY0Pzr_cA&bvm=bv.51773540,d.d2k&cad=rja


                
      was (Author: dagw):
    http://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CDwQFjAA&url=http%3A%2F%2Fciteseerx.ist.psu.edu%2Fviewdoc%2Fdownload%3Fdoi%3D10.1.1.56.6379%26rep%3Drep1%26type%3Dpdf&ei=3GUoUtbTN8uQ0QWh0oDYAw&usg=AFQjCNFme8BiQI59ZnxP68M6cnY0Pzr_cA&bvm=bv.51773540,d.d2k&cad=rja
                  
> Implement optimizer support for bushy trees.
> --------------------------------------------
>
>                 Key: DERBY-4327
>                 URL: https://issues.apache.org/jira/browse/DERBY-4327
>             Project: Derby
>          Issue Type: Improvement
>          Components: SQL
>            Reporter: Rick Hillegas
>              Labels: derby_triage10_10
>
> Currently, the optimizer only considers left-deep trees. For queries involving many tables, the best plan may be bushy. In this email thread, a user notes poor performance by Derby on queries involving 5 or more tables: http://www.nabble.com/Slow-performance-on-5-or-more-joins-in-a-star-schema-tt24708686.html

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