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From "Rick Hillegas (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DERBY-4327) Implement optimizer support for bushy trees.
Date Mon, 30 Nov 2015 17:52:10 GMT

    [ https://issues.apache.org/jira/browse/DERBY-4327?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15032158#comment-15032158
] 

Rick Hillegas commented on DERBY-4327:
--------------------------------------

I would repeat the feedback which I gave to Nirmal five years ago: I do not recommend this
issue as an introduction to the Derby optimizer. Thanks.

> 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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