BUG #4888: Removed brackets from Check Constraints expressions

The following bug has been logged online:

Bug reference:      4888
Logged by:          stalker
Email address:      chimera@bk.ru
PostgreSQL version: 8.3.7
Operating system:   Debian 4.0 (etch)
Description:        Removed brackets from Check Constraints expressions
Details:

I try to create Check Constraints for DB with Nested Set data model. When I
write complex validation rule with OR-operator - result Description is
incorrect.

CREATE TABLE Catalog
(
  id     integer,
  id_lft integer, -- nested set
  id_rgt integer,
);

ALTER TABLE Catalog
  ADD CONSTRAINT ctg_check_ns CHECK (id_lft > id_rgt OR (id_lft = 0 AND
id_lft = 0));

Result:
  'ctg_check_ns' Definition == "id_lft > id_rgt OR id_lft = 0 AND id_lft =
0".