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From "A B (JIRA)" <derby-...@db.apache.org>
Subject [jira] Updated: (DERBY-1681) Regression (wrong results): Join predicate can be ignored for left-most child in a chain of nested unions.
Date Fri, 11 Aug 2006 22:16:14 GMT
     [ http://issues.apache.org/jira/browse/DERBY-1681?page=all ]

A B updated DERBY-1681:

    Attachment: d1681_v1.patch

Attaching three things to this issue:

  1. A patch for the problem: d1681_v1.patch
  2. A patch for a test to verify the fix: d1681_test.patch
  3. A (short) description of the issue and the fix.

The reason I've separated the fix from the test is that the test case relies on database objects
that are included in the patch for DERBY-1633, and thus the test patch cannot be applied until
the patch for DERBY-1633 has been applied.

The actual fix to the problem, though--i.e. d1681_v1.patch--can be applied and committed independently
of DERBY-1633, and thus I've separated it out.

I ran derbyall on Red Hat Linux with ibm142 against SANE jars and there were no new failures.

Both patches are ready for review and commit (with the caveat just noted about the test case).

> 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_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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