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From "Dag H. Wanvik (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DERBY-532) Support deferrable constraints
Date Tue, 29 Apr 2014 00:38:20 GMT

    [ https://issues.apache.org/jira/browse/DERBY-532?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13983798#comment-13983798
] 

Dag H. Wanvik commented on DERBY-532:
-------------------------------------

With the latest commit, deferrable constraints ought to (prove me wrong!) work for

- unique/primary key constraints
- referential constraints (aka foreign key constraints)
- check constraints

I do not intend to add support for column NOT NULL constraints. Also, there is no support
yet for changing constraints to "not enforced", otherwise the standard semantics of SQL 2011
should apply. 

I intend to add a few more tests for foreign key constraints.


> Support deferrable constraints
> ------------------------------
>
>                 Key: DERBY-532
>                 URL: https://issues.apache.org/jira/browse/DERBY-532
>             Project: Derby
>          Issue Type: Improvement
>          Components: SQL
>            Reporter: Jörg von Frantzius
>            Assignee: Dag H. Wanvik
>              Labels: derby_triage10_11
>             Fix For: 10.11.0.0
>
>         Attachments: IndexDescriptor.html, IndexDescriptorImpl.html, IndexRowGenerator.html,
SortObserver.html, deferredConstraints.html, deferredConstraints.html, deferredConstraints.html,
deferredConstraints.html, deferredConstraints.html, derby-532-allow-pk-unique-1.diff, derby-532-allow-pk-unique-1.status,
derby-532-check-constraints-1.diff, derby-532-check-constraints-1.stat, derby-532-check-constraints-2.diff,
derby-532-check-constraints-2.stat, derby-532-fix-drop-not-nullable.diff, derby-532-fix-drop-not-nullable.status,
derby-532-fix-metadata-1.diff, derby-532-fix-metadata-1.status, derby-532-fk-1.diff, derby-532-fk-3.diff,
derby-532-fk-3.stat, derby-532-fk-4.diff, derby-532-fk-5.diff, derby-532-fk-5.stat, derby-532-fk-6.diff,
derby-532-fk-6.stat, derby-532-fk-7.diff, derby-532-fk-7.stat, derby-532-fk-baseline-2.diff,
derby-532-fk-baseline.diff, derby-532-import-1.diff, derby-532-import-1.status, derby-532-import-2.diff,
derby-532-import-3.diff, derby-532-import-3.status, derby-532-more-tests-1.diff, derby-532-more-tests-1.stat,
derby-532-nullableUniqueFix.diff, derby-532-nullableUniqueFix.status, derby-532-post-scan-1.diff,
derby-532-post-scan-1.stat, derby-532-post-scan-2.diff, derby-532-post-scan-2.stat, derby-532-post-scan-3.diff,
derby-532-post-scan-3.stat, derby-532-post-scan-4.diff, derby-532-post-scan-4.stat, derby-532-serializable-scan-1.diff,
derby-532-serializable-scan-2.diff, derby-532-serializable-scan-2.stat, derby-532-syntax-binding-dict-1.diff,
derby-532-syntax-binding-dict-1.status, derby-532-syntax-binding-dict-2.diff, derby-532-syntax-binding-dict-2.status,
derby-532-syntax-binding-dict-all-1.diff, derby-532-test-speedup.diff, derby-532-test-speedup.status,
derby-532-test-with-default-deferrable-all-over.diff, derby-532-testAlterConstraintInvalidation.diff,
derby-532-testAlterConstraintInvalidation.status, derby-532-unique-pk-1.diff, derby-532-unique-pk-1.status,
derby-532-unique-pk-2.diff, derby-532-unique-pk-3.diff, derby-532-unique-pk-3.status, derby-532-upgrade-1.diff,
derby-532-upgrade-1.status, derby-532-upgrade-1b.diff, derby-532-xa-1.diff, derby-532-xa-2.diff,
derby-532-xa-3.diff, derby-532-xa-3.status
>
>
> In many situations it is desirable to have constraints checking taking place only at
transaction commit time, and not before. If e.g. there is a chain of foreign key constraints
between tables, insert statements have to be ordered to avoid constraint violations. If foreign
key references are circular, the DML has to be split into insert statements and subsequent
update statements by the user.
> In other words, with deferred constraints checking, life is much easier for the user.
Also it can create problems with softwares such as object-relational mapping tools that are
not prepared for statement ordering and thus depend on deferred constraints checking.



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