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https://issues.apache.org/jira/browse/DERBY-3538?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12578635#action_12578635
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Thomas Nielsen commented on DERBY-3538:
---------------------------------------
Patch, comments and explaination is very good.
Running some tests on it now.
> 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: 10.0.2.0, 10.0.2.1, 10.1.1.0, 10.1.2.1, 10.1.3.1,
> 10.2.1.6, 10.2.2.0, 10.3.1.4, 10.3.2.1
> Reporter: A B
> Priority: Minor
> Attachments: d3538_notTested.diff
>
>
> 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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