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From "Bryan Pendleton (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-4406) Wrong order when using ORDER BY on non-deterministic function
Date Wed, 14 Apr 2010 13:38:50 GMT

    [ https://issues.apache.org/jira/browse/DERBY-4406?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12856891#action_12856891
] 

Bryan Pendleton commented on DERBY-4406:
----------------------------------------

Hi Nirmal,

It sounds like you have some ideas about some possible fixes.

Why don't you try writing a potential fix, and attach it to this issue as a patch proposal,
which will give us something more specific to discuss?

Also, when you write your fix, it would be great if you can also:
1) Run the current regression tests with your fix in place, and report the results
2) Include as part of your patch some additional regression test changes which
verify that this issue is fixed

If you need help enhancing the tests, just let us know what problems you encounter.


> Wrong order when using ORDER BY on non-deterministic function
> -------------------------------------------------------------
>
>                 Key: DERBY-4406
>                 URL: https://issues.apache.org/jira/browse/DERBY-4406
>             Project: Derby
>          Issue Type: Bug
>          Components: SQL
>    Affects Versions: 10.5.3.0, 10.6.0.0
>            Reporter: Knut Anders Hatlen
>            Assignee: C.S. Nirmal J. Fernando
>
> If I read the SQL standard correctly, a statement such as "select random() as r from
t order by random()" should be treated as "select random() as r from t order by r". Derby
does however generate a second, hidden random() column by which the rows are ordered.
> ij> create table t(x int);
> 0 rows inserted/updated/deleted
> ij> insert into t values 1,2,3,4,5;
> 5 rows inserted/updated/deleted
> ij> -- wrong result, not ordered by r
> ij> select random() as r from t order by random();
> R                     
> ----------------------
> 0.1285512465366495    
> 0.5116860880915798    
> 0.21060042130229073   
> 0.2506706923680875    
> 0.6378857329935494    
> 5 rows selected
> ij> -- correct result, ordered by r
> ij> select random() as r from t order by r;
> R                     
> ----------------------
> 0.0749025910679918    
> 0.07694931688380491   
> 0.1724114605785414    
> 0.2268758969382877    
> 0.31900450349277965   
> 5 rows selected

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