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https://issues.apache.org/jira/browse/DERBY-532?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13818998#comment-13818998
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Dag H. Wanvik commented on DERBY-532:
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Yes, the present patch solves this by throwing instead of saving duplicate key.
Not sure how this would work
with Mike's proposed approach - we do need this dynamic mode switching in order
to comply with the standard.
Maybe we could make a store API to provide language with the ability to decide
whether to insert or not (depending on constraint mode), e.g. return keys to
left and right of key (with locked rows) of the row to be inserted. I sort of
feel it would be a shame in any case to lose the improved performance early
checking would give... we have indexes in part for support constraints after
all.
> 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-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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