Changing foreign key referential actions in big databases

[Arthur Silva <arthurprs@xxxxxxxxx>]

Hi all, we're running a few Pg databases in production.

Ubuntu 14.04 x64

32 x64 cores
64GB to 256GB memory, depending on cluster

PostgreSQL 9.3.9 on x86_64-unknown-linux-gnu, compiled by gcc (Ubuntu 4.8.2-19ubuntu1) 4.8.2, 64-bit

FusionIO storage

We recently started looking into a long standing ticket to change some foreign keys referential actions from CASCADE to RESTRICT for our own safety. Everything else in the FK stays the same.

The problem is that running a query like the one bellow takes an exclusive lock for too long (order of minutes in some tables when testing against a backup db).

ALTER TABLE "partneracl"
DROP CONSTRAINT "partneracl_partner_fkey",
ADD CONSTRAINT "partneracl_partner_fkey"
FOREIGN KEY ("partner")
REFERENCES "partner"("name");

Is there any way to change the foreign key referential actions quickly and/or without an exclusive lock?
Is it safe(ish) to just update pg_constraint.confupdtype and pg_constraint.confdeltype for those?

Regards

--
Arthur Silva