Re: CASCADE/fkey order

You can benchmark your scenario with and without constraint using a tool
like nancy:

https://gitlab.com/postgres-ai/nancy

it lets you A/B test different configurations with your own scenarios or
using pgbench synthetic workloads.

-Michel

On Wed, Jul 22, 2020 at 9:27 AM Samuel Nelson <valczir(dot)darkvein(at)gmail(dot)com>
wrote:

> I checked, and changing the `bazinga_foo_bar` constraint to:
>
> alter table bazinga add constraint bazinga_foo_bar foreign key (foo_id,
> bar_id) references foo_bar (foo_id, bar_id) deferrable initially deferred;
>
> seems to fix it to work as we were expecting. Is that particularly
> costly? Should I only set the constraint to be deferred when we really
> need it? Would it be more efficient to perform the deletes explicitly
> within a transaction rather than relying on the cascades and deferring that
> one constraint?
>
> Our resident ex-Oracle DBA said that deferred constraints used to be
> heavily recommended against, but he also admitted that he hasn't kept up
> with that in the past 10 years.
>
> -Sam
>
> https://github.com/nelsam
>
> "As an adolescent I aspired to lasting fame, I craved factual certainty,
> and
> I thirsted for a meaningful vision of human life -- so I became a
> scientist.
> This is like becoming an archbishop so you can meet girls."
> -- Matt Cartmill
>
>
> On Wed, Jul 22, 2020 at 10:31 AM David G. Johnston <
> david(dot)g(dot)johnston(at)gmail(dot)com> wrote:
>
>> On Wed, Jul 22, 2020 at 8:24 AM Samuel Nelson <valczir(dot)darkvein(at)gmail(dot)com>
>> wrote:
>>
>>> Is there a way to force the delete to cascade to tables in a specific
>>> order?
>>>
>>
>> No really, but you can defer constraint checking.
>>
>> https://www.postgresql.org/docs/12/sql-set-constraints.html
>>
>> David J.
>>
>>
>