Re: [HACKERS] FOREIGN KEY !!!!!

At 09:30 PM 2/5/00 +0100, Jan Wieck wrote:
>> o Under RESTRICT, by contrast, the system realizes "ahead of
>>   time" that row R2 exists and will violate the constraint if
>>   R1 is deleted, and so rejects the DELETE out of hand.

>    That'd mean in last consequence, that RESTRICT actions aren't
>    DEFERRABLE, while the rest of their constraint definition is!

That's how I read it, too.  Pardon me while I run off to vomit in
the toilet.

>    Anyway,  cannot  work  with  the actual implementation of the
>    trigger queue, so we could either make RESTRICT and NO ACTION
>    identical (except for different ERROR messages), or leave the
>    SQL3 RESTRICT out of 7.0 while changing NO ACTION to fire the
>    message.

>    I'd  prefer  to have them identical in 7.0, because according
>    to Date they have no semantic difference,  so  it'll  buy  us
>    little  if we complicate the trigger stuff more than required
>    right now.

If others on the list agree, I think this is an excellent idea.  I
see no semantic difference that the application will see, either,
other than a difference in execution time.

Raising the exception before the delete or update seems more an efficiency
hack than anything, i.e. it's much less expensive to short-circuit the
delete/update rather than finish it, check afterwards, and roll it
back.




- Don Baccus, Portland OR  Nature photos, on-line guides, Pacific Northwest Rare Bird Alert Service and other goodies at http://donb.photo.net.