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From "Knut Anders Hatlen (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-4391) NullPointerException when comparing indexed column with result from a set operation
Date Wed, 30 Sep 2009 12:08:32 GMT

    [ https://issues.apache.org/jira/browse/DERBY-4391?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12760894#action_12760894
] 

Knut Anders Hatlen commented on DERBY-4391:
-------------------------------------------

It looks like the NPE is thrown if the left side of the set operation has a column which is
not a simple column reference. So the following queries (with expressions or constants on
the left side of the union) fail:

select * from t where a < (select 4 from t except select b from t)
select * from t where a < (select a+b from t except select 4 from t)
select * from t where a < (select a+b from t except select a from t)
select * from t where a < (select sum(a) from t intersect select b from t)

Whereas these don't raise a NPE:

select * from t where a < (select a from t intersect all select b from t)
select * from t where a < (select b from t except select 4 from t)
select * from t where a < (select a from t except select a+b from t)
select * from t where a < (select b from t union select sum(a) from t)

Also worth to notice is that the NPE is not raised if the binary arithmetic operator is =,
only if it is <, >, <= or >=.

> NullPointerException when comparing indexed column with result from a set operation
> -----------------------------------------------------------------------------------
>
>                 Key: DERBY-4391
>                 URL: https://issues.apache.org/jira/browse/DERBY-4391
>             Project: Derby
>          Issue Type: Bug
>          Components: SQL
>    Affects Versions: 10.2.2.0, 10.3.3.0, 10.4.2.0, 10.5.3.0, 10.6.0.0
>            Reporter: Knut Anders Hatlen
>
> I'm reporting this issue on behalf of Bernt M. Johnsen.
> If an indexed column is compared with a UNION query (or some other set operation), a
NullPointerException is raised, as can be seen by this sequence of statements in ij:
> ij> create table t(a int not null primary key, b int);
> 0 rows inserted/updated/deleted
> ij> select * from t where a < (values 4 union values 4);
> ERROR XJ001: Java exception: ': java.lang.NullPointerException'.

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