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From "Bryan Pendleton (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-2459) Ordering on a CASE-expression casues a NullPointerException when using a UNION
Date Fri, 25 May 2007 18:25:16 GMT

    [ https://issues.apache.org/jira/browse/DERBY-2459?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12499195
] 

Bryan Pendleton commented on DERBY-2459:
----------------------------------------

Three possible strategies to investigate, to start with:

1) Defer pull-up processing to later in CursorNode.bindStatement,
as was discussed (but not implemented) in DERBY-1861. As Army
noted in DERBY-1861, it's not obvious why pull-up processing was
positioned so early in bind processing.
2) Modify pull-up processing so that when it pulls a result column
into the RCL of a UnionNode, it also pulls that column into the
UnionNode's children (possibly recursively?)
3) Modify SetOperatorNode.buildRCL so that, rather than entirely
replacing the UnionNode's RCL with its left child's, it instead
merges the two RCL's, retaining the pulled-up columns but
replacing the other columns with those of the left child.

> Ordering on a CASE-expression casues a NullPointerException when using a UNION
> ------------------------------------------------------------------------------
>
>                 Key: DERBY-2459
>                 URL: https://issues.apache.org/jira/browse/DERBY-2459
>             Project: Derby
>          Issue Type: Bug
>          Components: SQL
>    Affects Versions: 10.1.3.1, 10.1.3.2, 10.2.1.6, 10.2.2.0, 10.2.2.1, 10.3.0.0
>         Environment: Java 1.5.0_06-b05 on Linux Ubuntu 5.10. Derby version 10.2.2
>            Reporter: Lars Gråmark
>         Assigned To: Bryan Pendleton
>
> When an order by clause involves a CASE-expression as seen below, a NullPointerException
is thrown. The error only occurs when two select statements are combined in a union (or union
all).
> select t1.id, CASE WHEN t2.value IS NOT NULL THEN t2.value ELSE t1.value END
> from A1 t1
> left outer join B1 t2 ON t2.id = t1.ref
> union all
> select t1.id, CASE WHEN t2.value IS NOT NULL THEN t2.value ELSE t1.value END
> from A2 t1
> left outer join B2 t2 ON t2.id = t1.ref
> order by CASE WHEN t2.value IS NOT NULL THEN t2.value ELSE t1.value END
> --Use the following statement to reproduce the problem:
> create table A1
> (
>    id char(1)
>   ,value int
>   ,ref char(1)
> );
> create table A2
> (
>    id char(1)
>   ,value int
>   ,ref char(1)
> );
> create table B1
> (
>    id char(1)
>   ,value int
> );
> create table B2
> (
>    id char(1)
>   ,value int
> );
> insert into A1 (id, value, ref) values ('a', 12, 'e');
> insert into A1 (id, value, ref) values ('b', 1, null);
> insert into A2 (id, value, ref) values ('c', 3, 'g');
> insert into A2 (id, value, ref) values ('d', 8, null);
> insert into B1 (id, value) values ('e', 4);
> insert into B1 (id, value) values ('f', 2);
> insert into B2 (id, value) values ('g', 5);

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