[GENERAL] drop check constraint

[Tamsin]

Hello,

Is it possible to drop a check constraint in any way without
dropping/recreating the table?  I've managed to drop foreign key constraints
by dropping the associated triggers, but check constraints don't seem to
create triggers and there isn't an alter table drop constraint command.  Is
there something I can do to the system tables?

(PostgreSQL 7.0.2)

Thanks for any ideas,
Tamsin