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From "Bryan Pendleton (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-2526) Wrong query results due to column ordering in UNION view
Date Fri, 06 Apr 2007 18:09:32 GMT

    [ https://issues.apache.org/jira/browse/DERBY-2526?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12487299
] 

Bryan Pendleton commented on DERBY-2526:
----------------------------------------

With those lines in FromBaseTable, the cost estimates are different, but the bottom line is
the same:

Good query plan:
Modifying access paths to use join order: 2,1,0 for 3 optimizables, with cost Level2CostEstimateImpl:
at 7363880, cost == 401.716, rowCount == 7.2, singleScanRowCount == 0.6000000000000001

Bad query plan:
Modifying access paths to use join order: 2,0,1 for 3 optimizables, with cost Level2CostEstimateImpl:
at 18796902, cost == 401.616, rowCount == 12.0, singleScanRowCount == 12.0

I'll look into this more later; I've got a few other things to do first.

> Wrong query results due to column ordering in UNION view
> --------------------------------------------------------
>
>                 Key: DERBY-2526
>                 URL: https://issues.apache.org/jira/browse/DERBY-2526
>             Project: Derby
>          Issue Type: Bug
>          Components: SQL
>    Affects Versions: 10.0.2.1, 10.1.3.1, 10.2.2.0, 10.3.0.0
>            Reporter: Bryan Pendleton
>         Attachments: badQuery.log, derby-2526.sql, goodQuery.log
>
>
> I think both select statements in the attached repro script should return 1 row, but
in fact the first statement returns 1 row and the second returns zero rows.
> The only difference between the two statements is that the columns in the UNION view
are listed in a different order (bvw vs. bvw2).
> This seems like a bug to me; the order of the columns in the view definition shouldn't
matter, should it? 
> As Army noted on the derby-dev list, the fact that this reproduces with 10.0 means that
it is not caused by some of the 10.2 optimizer changes. Something else is going wrong.

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