Diabling constraints

Hi,

I am wondering is there any way of disabling constraints that was
created after the table itself was created.

I know I can drop the trigger that the constraint creates.  However, I
need to make this change in several postgres database and it seems like
the the tgname that is required to remove the constraint is generate by
the system so I can't just go
    drop trigger "<tgname>" on <tablename> because tgname is different in
all the database I need to modify.

Any ideas in disabling or removing them without harding the tgname..
Thanks

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LL