Adriano dos Santos Fernandes wrote:

>> Adriano,
>>
>> Do you meant that the value should be only provided on insert, and
>> no update be allowed ?
>>
>>
> Yes and the value should be updatable in "on insert triggers".
> But not with UPDATE statement and in "on update triggers".

Currently, we only support a specific list of fields in grants statements
associated with UPDATE and REFERENCES. Isn't this what you are looking for?

create role cat;
grant update(a) on t to role cat;

Fields not specified can't be updated by users that attached to the db with
role cat.

C.