Re: OO and relation "impedance mismatch"

Tony Andrews wrote:

> Kenneth Downs wrote:

>> > Presumably you don't mean that the tables wouldn't ALSO have

>> > unique, foreign key constraints do you?
>>
>> Correct, they would not also have the constraints.  The purpose is to
>> completely control error reporting and have it behave the same way

>> all platforms, and declarative constraints don't let me do that.

so does a trigger. The constraint can be removed by an administrator and so can the trigger. They are functionally equivalent and offer precisely the same level of protection.

>
> - It is extremely difficult (if not impossible) to write such
> constraints in procedural code. How do you prevent 2 users
> simultaneously entering a record with the same "primary key" if you
> don't have a primary key (or unique) constraint? Do you lock the whole
> table during insert statements?

It is not hard to manage. It would be really hard and silly to do it by hand, coding all of those triggers, but that's why I generate the triggers out of the data dictionary.

>
> - Database constraints can be used by the optimizer to determine the
> best query plan

so can indexes, which have to be there anyway if you use triggers.

>
> No, what you are doing is throwing away decades of development by the
> DBMS vendors and making yourself decades of work, plus a database that
> won't perform as well as it should, and will likely have plenty of data
> corruption in it.
>
> IMHO, I suppose I'd better add!

Crucial crucial point: I do things this way because it is *easier* for me. If it took decades, I could not make a living because I do real development, not theoretical work.

Now, having made that blustery and possibly flame-inducing statement, I should add that work on my current vision began only a few months ago, so I cannot publish anything at this time, so I am completely vulnerable to the retort, "Show me the code, Ken!" Since I have not published so much as Version 0.1, claims made in this thread are totally my unsubstantiated opinion.

-- 
Kenneth Downs
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