Ok to flip pg_constraint.condeferrable on 9.1?

Hackers; as per $subject...

We have an FK defined on a table large enough and 24x7 as to make a
redefining of same constraint a painful solution.

Ran into a case where defining as deferrable initially immediate and
just running one batch job with deferred firing would solve a
concurrency problem that we discovered.

Grabbing a quick exclusive lock on the 2 related tables would not be a
problem if same might help avoid bad side-effects.

Developers are already working on a chunking solution to avoid the
long-running transaction that gave rise to this but I'd like to
consider this if it's not risky.

Comments?

--
Jerry Sievers
Postgres DBA/Development Consulting
e: postgres(dot)consulting(at)comcast(dot)net
p: 312.241.7800