Re: GSoC 2017: Foreign Key Arrays

On Tue, Jul 18, 2017 at 2:24 AM, Mark Rofail <markm(dot)rofail(at)gmail(dot)com> wrote:

> On Wed, Jul 12, 2017 at 12:53 AM, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com
> > wrote:
>>
>> We have one opclass for each type combination -- int4 to int2, int4 to
>> int4, int4 to int8, etc. You just need to add the new strategy to all
>> the opclasses.
>
>
> I tried this approach by manually declaring the operator multiple of
> times in pg_amop.h (src/include/catalog/pg_amop.h)
>
> so instead of the polymorphic declaration
> DATA(insert ( 2745 2277 2283 5 s 6108 2742 0 )); /* anyarray @>>
> anyelem */
>
> multiple declarations were used, for example for int4[] :
> DATA(insert ( 2745 1007 20 5 s 6108 2742 0 )); /* int4[] @>> int8 */
> DATA(insert ( 2745 1007 23 5 s 6108 2742 0 )); /* int4[] @>> int4 */
> DATA(insert ( 2745 1007 21 5 s 6108 2742 0 )); /* int4[] @>> int2 */
> DATA(insert ( 2745 1007 1700 5 s 6108 2742 0 ));/* int4[] @>> numeric */
>
> However, make check produced:
> could not create unique index "pg_amop_opr_fam_index"
> Key (amopopr, amoppurpose, amopfamily)=(6108, s, 2745) is duplicated.
>
> Am I implementing this the wrong way or do we need to look for another
> approach?
>

The problem is that you need to have not only opclass entries for the
operators, but also operators themselves. I.e. separate operators for
int4[] @>> int8, int4[] @>> int4, int4[] @>> int2, int4[] @>> numeric. You
tried to add multiple pg_amop rows for single operator and consequently get
unique index violation.

Alvaro, do you think we need to define all these operators? I'm not sure.
If even we need it, I think we shouldn't do this during this GSoC. What
particular shortcomings do you see in explicit cast in RI triggers queries?

------
Alexander Korotkov
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company