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From "Mike Matrigali (JIRA)" <j...@apache.org>
Subject [jira] [Comment Edited] (DERBY-532) Support deferrable constraints
Date Tue, 12 Nov 2013 22:45:17 GMT

    [ https://issues.apache.org/jira/browse/DERBY-532?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13820561#comment-13820561
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Mike Matrigali edited comment on DERBY-532 at 11/12/13 10:44 PM:
-----------------------------------------------------------------

i will look at this, though it does seem quite complicated.  Is it any less complicated to
prove correct if you do the check after the insert always?

For review I am first just going to concentrate on the algorithm described above.  If we all
agree on it working, then I will look at the code.  Hopefully the code will also have the
above description as comments somewhere.




was (Author: mikem):
i will look at this, though it does seem quite complicated.  Is it any less complicated to
prove correct if you do the check after the insert always?

> 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
>         Attachments: deferredConstraints.html, deferredConstraints.html, deferredConstraints.html,
deferredConstraints.html, 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-serializable-scan-1.diff, 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-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-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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