Re: patch for check constraints using multiple inheritance

On Fri, Jul 30, 2010 at 11:39 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Yeb Havinga <yebhavinga(at)gmail(dot)com> writes:
>> Regard the following lattice (direction from top to bottom):
>
>> 1
>> |\
>> 2 3
>>  \|\
>>   4 5
>>    \|
>>     6
>
>> When adding a constraint to 1, the proper coninhcount for that
>> constraint on relation 6 is 2. But the code currently counts to 3, since
>> 6 is reached by paths 1-2-4-5, 1-3-4-6, 1-3-5-6.
>
> Mph.  I'm not sure that 3 is wrong.  You have to consider what happens
> during a DROP CONSTRAINT, which as far as I saw this patch didn't
> address.

The behavior of DROP CONSTRAINT matches the fine documentation. The
behavior of ADD CONSTRAINT does not. Perhaps there's a definition of
coninhcount that would make 3 the right answer, but (a) I'm not sure
what that definition would be and (b) it's certainly not the one in
the manual.

--
Robert Haas
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