New relkind (was Re: [HACKERS] Exposing quals)

On Mon, Jul 07, 2008 at 06:46:29PM -0400, Andrew Dunstan wrote:
> >
> > On Mon, 2008-05-05 at 12:01 -0700, David Fetter wrote:
> >
> >> Please find attached the patch, and thanks to Neil Conway and
> >> Korry Douglas for the code, and to Jan Wieck for helping me
> >> hammer out the scheme above. Mistakes are all mine ;)
> >
> > I see no negative comments to this patch on -hackers.
> >
> > This was discussed here
> > http://wiki.postgresql.org/wiki/PgCon_2008_Developer_Meeting#SQL.2FMED
> > and I had understood the consensus to be that we would go ahead
> > with this?
> >
> > The notes say "Heikki doesn't think this is a long term solution",
> > but in the following discussion it was the *only* way of doing
> > this that will work with non-PostgreSQL databases. So it seems
> > like the way we would want to go, yes?
> >
> > So, can we add this to the CommitFest July page so it can receive
> > some substantial constructive/destructive comments?
> >
> > This could be an important feature in conjunction with Hot
> > Standby.
>
> The notes say at the end:
>
> "Jan thinks that showing the node tree will work better. But others
> don't agree with him -- it wouldn't work for PL/perlU. But Jan
> thinks it would work to give it a pointer to the parse tree and the
> range, we'd need to add an access function for the PL."
>
> For the record, I agree with Jan's suggestion of passing a pointer
> to the parse tree, and offline gave David a suggestion verbally as
> to how this could be handled for PL/PerlU.
>
> I don't think we should be tied too closely to a string
> representation, although possibly the first and simplest callback
> function would simply stringify the quals.

As I understand Jan's plan, the idea is to create a new relkind with
an exit to user code at leaf nodes in the plan tree. This would
require an API design for both user C code and for each PL to use, but
would then allow PostgreSQL's optimizer to work on JOINs, etc.

Jan, have I got that right so far? Do you have something in the way
of a rough patch, docs, etc. for this?

Cheers,
David.
--
David Fetter <david@fetter.org> http://fetter.org/
Phone: +1 415 235 3778 AIM: dfetter666 Yahoo!: dfetter
Skype: davidfetter XMPP: david.fetter@gmail.com

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