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From "Stefan Zeiger (JIRA)" <j...@apache.org>
Subject [jira] [Created] (DERBY-5911) WHERE condition getting pushed into sub-query with FETCH
Date Tue, 28 Aug 2012 11:19:07 GMT
Stefan Zeiger created DERBY-5911:
------------------------------------

             Summary: WHERE condition getting pushed into sub-query with FETCH
                 Key: DERBY-5911
                 URL: https://issues.apache.org/jira/browse/DERBY-5911
             Project: Derby
          Issue Type: Bug
          Components: SQL
    Affects Versions: 10.9.1.0
         Environment: Tested with Derby 10.9.1.0 on Windows 7 x64, Java 1.6.0_27-b07 server
            Reporter: Stefan Zeiger


Derby pushes query conditions down into subqueries with FETCH limits, thus creating wrong
results. Take the following snippet:

    CREATE TABLE COFFEES (COF_NAME VARCHAR(254),PRICE INTEGER);
    
    INSERT INTO COFFEES (COF_NAME,PRICE) VALUES ('Colombian',       5);
    INSERT INTO COFFEES (COF_NAME,PRICE) VALUES ('French_Roast',    5);
    INSERT INTO COFFEES (COF_NAME,PRICE) VALUES ('Colombian_Decaf', 20);
    
    select COF_NAME, PRICE from COFFEES order by COF_NAME fetch next 2 rows only;
    
    select * from (
      select COF_NAME, PRICE from COFFEES order by COF_NAME fetch next 2 rows only
    ) t where t.PRICE < 10;

The first query correctly returns the rows (Colombian,5), (Colombian_Decaf,20).

The second query (which filters the result of the first one) returns (Colombian,5), (French_Roast,5).
The row (French_Roast,5) should not be there since it is not a result of the first query.
It shows up because (supposedly) the filter condition has been evaluated before the fetch
limit.


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