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From "A B (JIRA)" <derby-...@db.apache.org>
Subject [jira] Commented: (DERBY-1681) Regression (wrong results): Join predicate can be ignored for left-most child in a chain of nested unions.
Date Mon, 28 Aug 2006 16:44:23 GMT
    [ http://issues.apache.org/jira/browse/DERBY-1681?page=comments#action_12431007 ] 
A B commented on DERBY-1681:

Thanks for commiting the new test case to trunk and 10.2, Mike.  Since the changes for DERBY-1633
have now been ported to 10.1 (thank you for that, too, Mike!), can the test case for this
issue go to 10.1, as well?  It should be a simple merge:

svn merge -r 437379:437380 http://svn.apache.org/repos/asf/db/derby/code/trunk

Also, one small note: it looks there's a typo in the Jira issue for the svn commit logs with
the d1681_test_v2.patch: there are a couple of references to "DERBY-1691" instead of "DERBY-1681".
 Perhaps these can be corrected?

> Regression (wrong results): Join predicate can be ignored for left-most child in a chain
of nested unions.
> ----------------------------------------------------------------------------------------------------------
>                 Key: DERBY-1681
>                 URL: http://issues.apache.org/jira/browse/DERBY-1681
>             Project: Derby
>          Issue Type: Bug
>          Components: SQL
>    Affects Versions:,,
>            Reporter: A B
>         Assigned To: A B
>             Fix For:,
>         Attachments: d1681_test.patch, d1681_test_v2.patch, d1681_v1.patch, DERBY-1681_v1.html
> If Derby chooses to do a join between two FromTables and the right table is a chain of
UNIONs, then the optimizer may choose to push the join predicate (if provided) down into the
UNION and to both children of every UNION in the chain.  But if the predicate cannot be pushed
to the children of any of the UNIONs (except the top-level one)  the predicate can end up
being ignored altogether with respect to that UNION's children.  The result is that query
execution can return rows that do not satisfy the predicate.
> This is a regression introduced in and thus it affects 10.1.3 and 10.2.  I came
across this while tracing through code for DERBY-1633.

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