[ http://issues.apache.org/jira/browse/DERBY-1681?page=all ]
A B reopened DERBY-1681:
------------------------
Looks like I was making changes the same time Mike was, and our changes
clashed. So I'm reopening (again) to correct fix-in and uncheck patch
available...
> 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: 10.1.3.1, 10.1.3.0, 10.2.1.0
> Reporter: A B
> Assigned To: A B
> Fix For: 10.2.1.0, 10.1.4.0, 10.3.0.0
>
> 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 10.1.2.4 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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