Update Enum Type Item (Label) in PostgreSQL

update

-- Update one label in custom enum type
UPDATE pg_enum SET enumlabel = 'new_value'
WHERE enumlabel = 'old_value' AND enumtypid = (
    SELECT oid FROM pg_type WHERE typname = 'enum_type'
);

-- Add new label in custom type avaliable since PostgreSQL 9.1
ALTER TYPE enum_type ADD VALUE 'new_value' BEFORE 'old_value';
ALTER TYPE enum_type ADD VALUE 'new_value' AFTER 'old_value';