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https://issues.apache.org/jira/browse/DERBY-2526?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12488534
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A B commented on DERBY-2526:
----------------------------
Just a knee-jerk reaction to the DistinctTest failure: I wonder if the
transitive closure is leading to alteration or removal of predicates that break
the conditions described here:
http://db.apache.org/derby/docs/dev/tuning/ctuntransform16279.html
For example, there is some talk about how Derby will remove equijoin predicates
as part of transitive closure at the bottom of this page:
http://db.apache.org/derby/docs/dev/tuning/rtuntransform866587.html
Maybe one of the equijoin predicates that is removed breaks the condition for
DISTINCT elimination?
As I said, that's just knee-jerk feedback. Apologies if it proves irrelevant...
> 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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