From: | Samuel Nelson <valczir(dot)darkvein(at)gmail(dot)com> |
---|---|
To: | "David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com> |
Cc: | pgsql-general <pgsql-general(at)postgresql(dot)org> |
Subject: | Re: CASCADE/fkey order |
Date: | 2020-07-22 16:03:14 |
Message-ID: | CAC7xaNcR2L74_enJFtDSsdAqQdm1ZT-8_T+dfuyp2zXdBqfPHw@mail.gmail.com |
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Thread: | |
Lists: | pgsql-general |
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
"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.
>
>
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