Changing foreign key referential actions in big databases

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");