Обсуждение: TODO improvements

This patch makes some minor improvements to the TODO list:

  * add URLs for some TODO items (I think we ought to try to associate
    at least one URL with each non-trivial TODO item)

  * re-add a TODO item for an "estimated count"-like facility

  * add a TODO item for considering changing how equality comparisons
    treat NaN values, per recent discussion

Barring any objections, I'll apply this to HEAD tomorrow.

-Neil

Neil Conway <neilc@samurai.com> writes:
>   * add a TODO item for considering changing how equality comparisons
>     treat NaN values, per recent discussion

Seems like a complete nonstarter, unfortunately.  btree requires the
datatype to have a total order, and I can't see that changing, so NaN
loses.

            regards, tom lane

On Mon, 2007-01-15 at 13:29 -0500, Tom Lane wrote:
> Seems like a complete nonstarter, unfortunately.  btree requires the
> datatype to have a total order, and I can't see that changing, so NaN
> loses.

Well, yeah, that would be the major impediment to implementing it. We
could just not define a total order on types with a NaN value, but I
agree that's probably not a net win... :)

BTW, it seems that while Oracle provides an IS NAN construct, they also
treat NaN as equal to itself (which makes me question why they added IS
NAN in the first place). So perhaps it is sufficient to leave things as
they are...

-Neil

Neil Conway wrote:
> On Mon, 2007-01-15 at 13:29 -0500, Tom Lane wrote:
> > Seems like a complete nonstarter, unfortunately.  btree requires the
> > datatype to have a total order, and I can't see that changing, so NaN
> > loses.
>
> Well, yeah, that would be the major impediment to implementing it. We
> could just not define a total order on types with a NaN value, but I
> agree that's probably not a net win... :)
>
> BTW, it seems that while Oracle provides an IS NAN construct, they also
> treat NaN as equal to itself (which makes me question why they added IS
> NAN in the first place). So perhaps it is sufficient to leave things as
> they are...

Agreed.  We do have something in the documentation about it now too.

--
  Bruce Momjian   bruce@momjian.us
  EnterpriseDB    http://www.enterprisedb.com

  + If your life is a hard drive, Christ can be your backup. +

On Mon, 2007-01-15 at 13:41 -0500, Neil Conway wrote:
> BTW, it seems that while Oracle provides an IS NAN construct, they also
> treat NaN as equal to itself (which makes me question why they added IS
> NAN in the first place). So perhaps it is sufficient to leave things as
> they are...

Patch applied, without the NaN TODO item.

-Neil