Re: PostgreSQL Limits and lack of documentation about them.

On Thu, 29 Nov 2018 at 07:06, Peter Eisentraut
<peter(dot)eisentraut(at)2ndquadrant(dot)com> wrote:
>
> That last sentence about the dropped columns is confusing to me:
>
> + <para>
> + Columns which have been dropped from the table also contribute to the
> + maximum column limit, although the dropped column values for newly
> + created tuples are internally marked as NULL in the tuple's null
> bitmap,
> + which does occupy space.
> + </para>
>
> So the dropped columns matter, but they are null, but the nulls matter
> too. What are we really trying to say here? Maybe this:
>
> Columns which have been dropped from the table also contribute to the
> maximum column limit. Moreover, although the dropped column values for
> newly created tuples are internally marked as NULL in the tuple's null
> bitmap, the null bitmap also occupies space.

I'd say that's a small improvement that's worth making. I've attached
a patch using your reformed version of that paragraph.

--
David Rowley http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services