Re: minimal update

[Andrew Dunstan <andrew(at)dunslane(dot)net>]

Tom Lane wrote:
> Andrew Dunstan <andrew(at)dunslane(dot)net> writes:
>   
> > How does this look?
> >     
>
>   
> >     if (newtuple->t_len == oldtuple->t_len &&
> >         newtuple->t_data->t_hoff == oldtuple->t_data->t_hoff &&
> >         HeapTupleHeaderGetNatts(newtuple) == HeapTupleHeaderGetNatts(oldtuple) &&
> >         (newtuple->t_data->t_infomask & (HEAP_HASOID|HEAP_HASNULL)) == (oldtuple->t_data->t_infomask & (HEAP_HASOID|HEAP_HASNULL)) &&
> >         memcmp(newtuple->t_data + offsetof(HeapTupleHeaderData, t_bits),
> >                oldtuple->t_data + offsetof(HeapTupleHeaderData, t_bits)
> >                newtuple->t_len - offsetof(HeapTupleHeaderData, t_bits)) == 0)
> >     
>
>   
> >       rettuple = NULL;
> >     
>
> Looks sane.  It might be even saner if you compare all of the
> non-visibility-related infomask bits, viz
>
> 	(newtuple->t_data->t_infomask & ~HEAP_XACT_MASK) ==
> 	(oldtuple->t_data->t_infomask & ~HEAP_XACT_MASK)
>
> rather than just HASOID and HASNULL.
>
> 			
>   

Sadly, the memcmp is failing on my test ("update foo set bar = bar") on 
8.2. Looks like I'm in for weekend with my fave debugger :-(

cheers

andrew