Re: WIP: generalized index constraints

On Mon, Jul 06, 2009 at 11:56:41AM +0100, Simon Riggs wrote:
> On Sun, 2009-07-05 at 17:28 -0700, Jeff Davis wrote:
> > This is a follow up to my old proposal here:
> >
> > http://archives.postgresql.org/pgsql-hackers/2008-06/msg00404.php
> >
>
> > Any input is appreciated (design problems, implementation,
> > language ideas, or anything else). I'd like to get it into shape
> > for the July 15 commitfest if no major problems are found.
>
> I was concerned that your definition of concurrently inserted didn't
> seem to match the size of the shared memory array required.
>
> How will you cope with a large COPY? Surely there can be more than
> one concurrent insert from any backend?
>
> It would be useful to see a real example of what this can be used
> for.

Constraints like "these intervals can't overlap" would be one. It's
handy in calendaring applications, for example.

> I think it will be useful to separate the concepts of a constraint
> from the concept of an index. It seems possible to have a UNIQUE
> constraint that doesn't help at all in locating rows, just in
> proving that the rows are unique.

Interesting idea. Are you thinking of this in terms of things the
planner can do once it knows a set is all distinct values, or...?

Cheers,
David.
--
David Fetter <david(at)fetter(dot)org> http://fetter.org/
Phone: +1 415 235 3778 AIM: dfetter666 Yahoo!: dfetter
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