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From "Mike Matrigali (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DERBY-532) Support deferrable constraints
Date Tue, 12 Nov 2013 22:27:17 GMT

    [ https://issues.apache.org/jira/browse/DERBY-532?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13820562#comment-13820562

Mike Matrigali commented on DERBY-532:

question:  Is it possible for 2 transactions to be operating at the same time on a deferrable
constraint and in one case the checking is deferred and in the 2nd case the checking is immediate?

> 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,
> 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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