Tom Lane wrote:
> Andrew Dunstan <andrew@dunslane.net> writes:
>
>> Tom Lane wrote:
>>
>>> A BEFORE UPDATE trigger would be better, and probably hardly more
>>> expensive than a wired-in facility (especially if you were willing to
>>> write it in C).
>>>
>
>
>> Yes. I also prefer the trigger idea to a rule because triggers are easy
>> to enable and disable. It's still a lot of work for what must be a
>> common want, though. Could it be done generically?
>>
>
> Well, you could write the trigger in C and it'd work for any table.
> I think it could be as simple as a memcmp of the tuples' data areas,
> since we now require padding bytes to be 0 ...
>
>
>
Something like this fragment?
newtuple = trigdata->tg_newtuple; oldtuple = trigdata->tg_trigtuple; rettuple = newtuple;
if (newtuple->t_len == oldtuple->t_len && newtuple->t_data->t_hoff == oldtuple->t_data->t_hoff &&
memcmp(GETSTRUCT(newtuple),GETSTRUCT(oldtuple), newtuple->t_len - newtuple->t_data->t_hoff) == 0) rettuple
=NULL;
return PointerGetDatum(rettuple);
Also, when did we first require padding bytes to be 0?
cheers
andrew
