Re: best way to fetch next/prev record based on index

On Tue, 27 Jul 2004, Merlin Moncure wrote:

> Greg Stark wrote:
> > > > do it for multi-column keys. It seems it would be nice if some
> syntax
> > > > similar to (a,b,c) > (a1,b1,c1) worked for this.
> > Hum. It would seem my intuition matches the SQL92 spec and Postgres
> gets
> > this
> > wrong.
> [...]
> > Even if Postgres did this right I'm not sure that would solve your
> index
> > woes.
> > I imagine the first thing Postgres would do is rewrite it into regular
> > scalar
> > expressions. Ideally the optimizer should be capable of then deducing
> from
> > the
> > scalar expressions that an index scan would be useful.
>
> Wow. For once, the standard is my friend. Well, what has to be done?
> :) Does pg do it the way it does for a reason? From the outside it
> seems like the planner would have an easier job if it can make a field
> by field comparison.
>
> Would a patch introducing the correct behavior (per the standard) be
> accepted? It seems pretty complicated (not to mention the planner
> issues).

Given the comment on make_row_op,
/*
* XXX it's really wrong to generate a simple AND combination for < <=
* > >=. We probably need to invent a new runtime node type to handle
* those correctly. For the moment, though, keep on doing this ...
*/
I'd expect it'd be accepted.