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From "Kathey Marsden (JIRA)" <j...@apache.org>
Subject [jira] Created: (DERBY-4046) PredicatePushdownTest does not properly test for predicate pushdown in all cases
Date Mon, 02 Feb 2009 18:52:01 GMT
PredicatePushdownTest does not properly  test for predicate pushdown  in all cases
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                 Key: DERBY-4046
                 URL: https://issues.apache.org/jira/browse/DERBY-4046
             Project: Derby
          Issue Type: Bug
          Components: Test
    Affects Versions: 10.5.0.0
            Reporter: Kathey Marsden


In DERBY-3819 Knut commented that the JUnit test PredicatePushdownTest is no longer properly
testing predicate pushdown after conversion.
https://issues.apache.org/jira/browse/DERBY-3819?focusedCommentId=12669371#action_12669371

There is a comment in the test:
     // [We]can tell if a predicate has been "pushed" by looking at
        // the query plan information for the tables in question:
        // if the table has an index on a column that is used as
        // part of the pushed predicate, then the optimizer will
        // (for these tests) do an Index scan instead of a Table
        // scan. If the table does not have such an index then the
        // predicate will show up as a "qualifier" for a Table
        // scan. In all of these tests T3 and T4 have appropriate
        // indexes, so if we push a predicate to either of those
        // tables we should see index scans. Neither T1 nor T2 has
        // indexes, so if we push a predicate to either of those
        // tables we should see a qualifier in the table scan
        // information.

So I think that means in the case of index scans our checks are ok, but for table scans we
should also be checking the qualifiers.  The join strategy checks  are not really relevant
except that hash join prevents predicate pushdown.





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