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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-3944) Add optimization rules to reorder Cartesian products and joins
Date Tue, 14 Jun 2016 13:10:01 GMT

    [ https://issues.apache.org/jira/browse/FLINK-3944?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15329467#comment-15329467
] 

ASF GitHub Bot commented on FLINK-3944:
---------------------------------------

Github user fhueske commented on the issue:

    https://github.com/apache/flink/pull/2098
  
    merging


> Add optimization rules to reorder Cartesian products and joins
> --------------------------------------------------------------
>
>                 Key: FLINK-3944
>                 URL: https://issues.apache.org/jira/browse/FLINK-3944
>             Project: Flink
>          Issue Type: Bug
>          Components: Table API
>    Affects Versions: 1.1.0
>            Reporter: Fabian Hueske
>            Assignee: Fabian Hueske
>            Priority: Critical
>             Fix For: 1.1.0
>
>
> Currently, we do not support the execution of Cartesian products. 
> Because we do not optimize the order of joins (due to missing statistics), joins are
executed in the order in which they are specified. This works well for the Table API, however
it can be problematic in case of SQL queries where the order of tables in the FROM clause
should not matter.
> In case of SQL queries, it can happen that the optimized plan contains Cartesian products
because joins are not reordered. If we add optimization rules that switch Cartesian products
and joins, such situations can be resolved.



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