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https://issues.apache.org/jira/browse/DERBY-2526?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12492523
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Bryan Pendleton commented on DERBY-2526:
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I tried various experiments toward alternates #1 and #2 from the previous
comment, and only succeeding in creating non-operational code. These
sections of the SelectNode code seem delicate, and the code can't
be re-arranged easily; it all seems to work in exactly this order.
Now I'm thinking I should investigate the transitive closure code more
carefully, to see if there is a way to revise it so that it isn't so sensitive
to the column re-ordering but rather can recognize transitive closures
based on the original expressions.
> 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
> Assigned To: Bryan Pendleton
> Attachments: badQuery.log, derby-2526.sql, DistinctTestNotes.txt,
> firstTryPatch.diff, 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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