Details
Major Description
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.