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From "A B (JIRA)" <j...@apache.org>
Subject [jira] Created: (DERBY-3538) NullPointerException during execution for query with LEFT OUTER JOIN whose inner table selects all constants.
Date Fri, 14 Mar 2008 05:27:24 GMT
NullPointerException during execution for query with LEFT OUTER JOIN whose inner table selects
all constants.
-------------------------------------------------------------------------------------------------------------

                 Key: DERBY-3538
                 URL: https://issues.apache.org/jira/browse/DERBY-3538
             Project: Derby
          Issue Type: Bug
          Components: SQL
    Affects Versions: 10.3.2.1, 10.3.1.4, 10.2.2.0, 10.2.1.6, 10.1.3.1, 10.1.2.1, 10.1.1.0,
10.0.2.1, 10.0.2.0
            Reporter: A B
            Priority: Minor


For a query having a LEFT OUTER JOIN such that the right, or "inner", table is a SELECT subquery
whose result column list consists entirely of constants, Derby may throw an execution-time
NPE while trying to apply the join predicate.  I say "may" because it depends on which join
strategy the optimizer chooses.

Using optimizer overrides I was able to reproduce this problem against trunk with the following
(admittedly nonsense) query:

  create table t1 (i int, j int);
  insert into t1 values (-1, -2), (-2, -4), (-3, -9);

  select * from
    t1 left outer join
    (select -1 a, 1 b from t1) x0 --DERBY-PROPERTIES joinStrategy=NESTEDLOOP
   on x0.a = t1.i;

I          |J          |A          |B
-----------------------------------------------
-1         |-2         |-1         |1
-1         |-2         |-1         |1
-1         |-2         |-1         |1
ERROR 38000: The exception 'java.lang.NullPointerException' was thrown while evaluating an
expression.
ERROR XJ001: Java exception: ': java.lang.NullPointerException'.

Running the same query also failed with the same NPE on 10.0.2.1, even though optimizer overrides
don't exist there.  So I'm marking all known releases to be affected by this issue.

Note: while this particular query may not make much sense, I have seen a user with a very
large, auto-generated query that, when executed, fails due to this problem.  So it is worth
investigating...

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