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From "Dag H. Wanvik (JIRA)" <j...@apache.org>
Subject [jira] [Comment Edited] (DERBY-532) Support deferrable constraints
Date Tue, 19 Nov 2013 13:49:20 GMT

    [ https://issues.apache.org/jira/browse/DERBY-532?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13826517#comment-13826517
] 

Dag H. Wanvik edited comment on DERBY-532 at 11/19/13 1:47 PM:
---------------------------------------------------------------

(re SortObserver & friends): I think the changes are pretty small, and the alternative
would be to make separate sorting passes (one for each deferrable constraint/index on a table)
with new code to check the deferrables; not convinced that's worth the extra amount of code
and redundancy. For the moment, I'd like to keep these changes.


was (Author: dagw):
(re SortObserver & friends): I think the changes are pretty small, and the alternative
would be to make separate sorting passes (one for each index on a table) with new code to
check the deferrables; not convinced that's worth the extra amount of code and redundancy.
For the moment, I'd like to keep these changes.

> 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-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-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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