Re: Suggested TODO: allow ALTERing of typemods without heap/index rebuild

On Mon, Jun 1, 2009 at 9:49 PM, Jeff Davis <pgsql(at)j-davis(dot)com> wrote:
>
>
> NUMERIC(x, y) comes to mind, although that might be a more dangerous
> case. If you turn a NUMERIC(5,0) into a NUMERIC(5,1), then '1.2' may be
> stored as either '1' or '1.2' depending on whether you did the insert
> before or after the change. That's because, with NUMERIC, it's not
> really a constraint, but a rule for rounding.

Well it's not like rewriting the table is going to accomplish anything though...

> There may be other interesting cases involving constraints. For
> instance, if you have CHECK(i < 200), you should be able to add CHECK(i
> < 1000) without an exclusive lock or recheck. Then, with an exclusive
> lock, you can remove the original tighter constraint, but at least it
> wouldn't have to recheck the entire table.

We have the infrastructure for this kind of check actually, it's the
same kind of thing we do for partition exclusion...

--
greg