Robert Haas <robertmhaas@gmail.com> writes:
> On Fri, Mar 31, 2017 at 2:32 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> It just seems way too dangerous.
> So, we end up with heap tuples with different numbers of attributes
> all the time, whenever you add a column. It works fine - on decoding,
> the additional columns will be treated as null (unless somebody
> commits Serge Rielau's patch, which regrettably nobody has gotten
> around to reviewing). Why is this case different?
The reason it works fine for heap tuples is that heap tuple headers
explicitly record the number of attributes in the tuple. Index
tuples don't.
regards, tom lane