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Date: Wed, 16 Jul 2014 20:41:05 +0000 (UTC)
From: "Rick Hillegas (JIRA)" <jira@apache.org>
To: derby-dev@db.apache.org
Message-ID: <JIRA.12727754.1405538862326.57111.1405543265444@arcas>
In-Reply-To: <JIRA.12727754.1405538862326@arcas>
References: <JIRA.12727754.1405538862326@arcas>
Subject: [jira] [Commented] (DERBY-6668) Truncating a table may silently
 violate a deferred foreign key.
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    [ https://issues.apache.org/jira/browse/DERBY-6668?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14064052#comment-14064052 ] 

Rick Hillegas commented on DERBY-6668:
--------------------------------------

I would support the meat-ax approach of forbidding TRUNCATE on referenced tables, per the Standard. We would need a release note to flag the backward incompatibility.

> Truncating a table may silently violate a deferred foreign key.
> ---------------------------------------------------------------
>
>                 Key: DERBY-6668
>                 URL: https://issues.apache.org/jira/browse/DERBY-6668
>             Project: Derby
>          Issue Type: Bug
>          Components: SQL
>    Affects Versions: 10.11.0.0
>            Reporter: Rick Hillegas
>
> If you truncate a table which is referenced by a deferred foreign key, orphaned tuples are left in the foreign table. That is, the foreign key is violated but no exception is raised.
> Since table truncation involves changing conglomerate ids, this may be another case of derby-6665. Or this may be a new bug.
> The following script shows this behavior:
> {noformat}
> connect 'jdbc:derby:memory:db;create=true';
> create table tunique
> (
>   a int not null unique
> );
> create table tref
> (
>   a int references tunique( a ) initially deferred
> );
> insert into tunique values ( 1 );
> insert into tref values ( 1 );
> truncate table tunique;
> -- the unique table is empty
> select * from tunique;
> -- but the table which references it has a row
> select * from tref;
> {noformat}


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