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From "Dag H. Wanvik (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DERBY-6559) A immediate Fk constraint blows up iff its referenced PK is deferred and we delete a duplicate
Date Mon, 02 Jun 2014 22:43:02 GMT

    [ https://issues.apache.org/jira/browse/DERBY-6559?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14015992#comment-14015992
] 

Dag H. Wanvik commented on DERBY-6559:
--------------------------------------

But see [limitation on FK with deferrable pK here|https://issues.apache.org/jira/secure/EditComment!default.jspa?id=12713983&commentId=14015985]

> A immediate Fk constraint blows up iff its referenced PK is deferred and we delete a
duplicate
> ----------------------------------------------------------------------------------------------
>
>                 Key: DERBY-6559
>                 URL: https://issues.apache.org/jira/browse/DERBY-6559
>             Project: Derby
>          Issue Type: Bug
>          Components: SQL
>            Reporter: Dag H. Wanvik
>            Assignee: Dag H. Wanvik
>             Fix For: 10.11.0.0
>
>         Attachments: derby-6559.diff, derby-6559.status
>
>
> Cf the following test case:
> {code:title=testFKPlusUnique|borderStyle=solid}
>     /**
>      * The referenced constraint (in the referenced table) is also a deferred
>      * (unique/ok) constraint.
>      * 
>      * @throws SQLException 
>      */
>     public void testFKPlusUnique() throws SQLException {
>         Statement s = createStatement(
>                 ResultSet.TYPE_FORWARD_ONLY, ResultSet.CONCUR_UPDATABLE);
>         
>         try {
>             s.executeUpdate(
>                 "create table ref_t(i int, " +
>                 "    constraint ct primary key(i) deferrable initially deferred)");
>             s.executeUpdate(
>                 "create table t(i int unique not null, " +
>                 "    constraint c foreign key (i) references ref_t(i) " +
>                 "    deferrable initially immediate)");
>             
>             s.executeUpdate("insert into ref_t values 1,1");
>             s.executeUpdate("insert into t values 1");
>             
>             // Now, the child (referencing table) is referencing one of the the
>             // rows whose value is 1, so the reference is potentially suspect.
>             
>             // What happens when we delete the one copy before commit?
>             ResultSet rs = s.executeQuery("select * from ref_t");
>             rs.next();
>             
>             // Will this delete blow up? Hopefully not, here is another row
>             // that would satisfy the constraint.
>             rs.deleteRow();
>             
>             // Now there should be only one left, so the referenced table is
>             // OK.
>             commit();
>             :
> {code}
> Now, the constraint C throws when we do the "rs.deleteRow" above. But since there is
(still) a row satisfying the FK, albeit a duplicate, I believe it should not.



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