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From "Rick Hillegas (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DERBY-6668) Truncating a table may silently violate a deferred foreign key.
Date Wed, 16 Jul 2014 22:29:06 GMT

    [ https://issues.apache.org/jira/browse/DERBY-6668?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14064255#comment-14064255
] 

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

Note that even if the tables are empty, the TRUNCATE is not allowed on 10.10.2.0 (for the
non-deferabble constraints allowed in that release). So there should be no backward compatibility
problem and no need for a release note.

> 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
>            Assignee: Rick Hillegas
>         Attachments: derby-6668-01-aa-disallowTruncateOnReferencedTable.diff
>
>
> 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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