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From "Rick Hillegas (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DERBY-6004) Make it possible for table functions to declare that they return sorted results and make the optimizer exploit this information.
Date Mon, 26 Nov 2012 14:20:58 GMT

    [ https://issues.apache.org/jira/browse/DERBY-6004?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13503794#comment-13503794
] 

Rick Hillegas commented on DERBY-6004:
--------------------------------------

One issue we would want to consider is what to do if the table function lies. With restricted
table functions, the restriction is redundantly applied by Derby outside the table function,
so Derby returns correct results even when the table function lies. However, part of what
we want to achieve with ordered results is to eliminate unnecessary sort nodes.

One solution to this problem would be to attach a filter to the result stream of the table
function. The filter would raise an exception if it encountered an out-of-order tuple.
                
> Make it possible for table functions to declare that they return sorted results and make
the optimizer exploit this information.
> --------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: DERBY-6004
>                 URL: https://issues.apache.org/jira/browse/DERBY-6004
>             Project: Derby
>          Issue Type: Improvement
>          Components: SQL
>    Affects Versions: 10.10.0.0
>            Reporter: Rick Hillegas
>
> A derby-dev discussion has highlighted the need for table functions to return sorted
results which the optimizer can exploit. See http://old.nabble.com/Have-Derby-Network-Server-having-an-out-of-memory-%28PermGen%29-to34704415.html#a34706722

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