Re: att_isnull

Alvaro Herrera <alvherre@2ndquadrant.com> writes:
> Yeah, I've noticed this inconsistency too.  I doubt we want to change
> the macro definition or its name, but +1 for expanding the comment.
> Your proposed wording seems sufficient.

+1

>> There is some kind of broader confusion here, I think, because we
>> refer in many places to the "null bitmap" but it's actually not a
>> bitmap of which attributes are null but rather of which attributes are
>> not null.  That is confusing in and of itself, and it's also not very
>> intuitive that it uses exactly the opposite convention from what we do
>> with datum/isnull arrays.

> I remember being bit by this inconsistency while fixing data corruption
> problems, but I'm not sure what, if anything, should we do about it.
> Maybe there's a perfect spot where to add some further documentation
> about it (a code comment somewhere?) but I don't know where would that
> be.

It is documented in the "Database Physical Storage" part of the docs,
but no particular emphasis is laid on the 1-vs-0 convention.  Maybe
a few more words there are worthwhile?

            regards, tom lane