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https://issues.apache.org/jira/browse/DERBY-532?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13814088#comment-13814088
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Mike Matrigali commented on DERBY-532:
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i totally missed that this project was implementing yet another btree type, so
sorry for late review. I am still
looking at detail, but wondering if you ever considered any solution that did
not require special case code
in the btree. I would like to understand what would be the problem with
implementing deferred constraints
using existing "duplicate" btrees with no changes, and then do all deferred
contraint checking in the sql
layer doing probes to ascertain constraint consistency using existing access
interfaces (with maybe something
more specialized if that allows for faster path).
I know you are following a path that the "unique" with duplicate code followed.
I have regretted that approach
since it was implemented. The project resulted in many bugs because of the
complication involved in twisting
the code to do something that it really did not want to do.
> 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-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-xa-1.diff, derby-532-xa-2.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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