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Date: Sat, 28 Oct 2006 09:15:17 -0700 (PDT)
From: "Bryan Pendleton (JIRA)" <jira@apache.org>
To: derby-dev@db.apache.org
Subject: [jira] Commented: (DERBY-2008) NullPointerException with 2-argument
 SUBSTR() call in GROUP BY clause.
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    [ http://issues.apache.org/jira/browse/DERBY-2008?page=comments#action_12445387 ] 
            
Bryan Pendleton commented on DERBY-2008:
----------------------------------------

Hi Yip, I was just wondering: I see that TernaryOperatorNode is used for a few
other cases, besides just SUBSTR:  TRIM, LOCATE, LIKE, TIMESTAMPADD, 
and TIMESTAMPDIFF all seem to be TernaryOperatorNodes.

How does your patch affect the behavior of these functions? 

I suppose that if it had any affect at all, it would be to prevent similar NPE bugs
when one of these functions was used in an way which provoked an isEquivalent()
call for a case where the RHS of the Ternary was NULL.

I think the patch is fine, I'm just wondering whether it fixes any more problems
than just the SUBSTR-in-a-GROUP-BY case that is noted in the description.


> NullPointerException with 2-argument SUBSTR() call in GROUP BY clause.
> ----------------------------------------------------------------------
>
>                 Key: DERBY-2008
>                 URL: http://issues.apache.org/jira/browse/DERBY-2008
>             Project: Derby
>          Issue Type: Bug
>          Components: SQL
>    Affects Versions: 10.2.1.6, 10.3.0.0
>            Reporter: A B
>         Assigned To: Yip Ng
>            Priority: Minor
>         Attachments: derby2008-trunk-diff01.txt, derby2008-trunk-stat01.txt
>
>
> The following query, which fails with a syntax error in 10.1.3 (because functions are not allowed in a GROUP BY expression for 10.1) fails with a NullPointerException in 10.2 and in the codeline (10.3):
> create table dt (vc varchar(30)); 
> insert into dt values ('1928-09-21'), ('1903-12-08'); 
> select substr(vc, 3) from dt group by substr(vc, 3); 
> Result (on trunk) is:
> java.lang.NullPointerException
> 	at org.apache.derby.impl.sql.compile.TernaryOperatorNode.isEquivalent(TernaryOperatorNode.java:924)
> 	at org.apache.derby.impl.sql.compile.GroupByList.findGroupingColumn(GroupByList.java:244)
> 	at org.apache.derby.impl.sql.compile.VerifyAggregateExpressionsVisitor.skipChildren(VerifyAggregateExpressionsVisitor.java:146)
> 	at org.apache.derby.impl.sql.compile.TernaryOperatorNode.accept(TernaryOperatorNode.java:497)
> 	at org.apache.derby.impl.sql.compile.ResultColumn.accept(ResultColumn.java:1515)
> 	at org.apache.derby.impl.sql.compile.QueryTreeNodeVector.accept(QueryTreeNodeVector.java:159)
> 	at org.apache.derby.impl.sql.compile.SelectNode.bindExpressions(SelectNode.java:619)
> 	at org.apache.derby.impl.sql.compile.FromSubquery.bindExpressions(FromSubquery.java:262)
> 	at org.apache.derby.impl.sql.compile.FromList.bindExpressions(FromList.java:337)
> 	at org.apache.derby.impl.sql.compile.SelectNode.bindExpressions(SelectNode.java:500)
> 	at org.apache.derby.impl.sql.compile.DMLStatementNode.bindExpressions(DMLStatementNode.java:249)
> 	at org.apache.derby.impl.sql.compile.DMLStatementNode.bind(DMLStatementNode.java:162)
> 	at org.apache.derby.impl.sql.compile.CursorNode.bind(CursorNode.java:253)
> 	at org.apache.derby.impl.sql.GenericStatement.prepMinion(GenericStatement.java:345)
> 	at org.apache.derby.impl.sql.GenericStatement.prepare(GenericStatement.java:119)
> 	at org.apache.derby.impl.sql.conn.GenericLanguageConnectionContext.prepareInternalStatement(GenericLanguageConnectionContext.java:745)
> 	at org.apache.derby.impl.jdbc.EmbedStatement.execute(EmbedStatement.java:568)
> 	at org.apache.derby.impl.jdbc.EmbedStatement.execute(EmbedStatement.java:517)

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