From: | Martijn van Oosterhout <kleptog(at)svana(dot)org> |
---|---|
To: | Zoltan Boszormenyi <zb(at)cybertec(dot)at> |
Cc: | Gregory Stark <stark(at)enterprisedb(dot)com>, Tatsuo Ishii <ishii(at)postgresql(dot)org>, David Fetter <david(at)fetter(dot)org>, PG Hackers <pgsql-hackers(at)postgresql(dot)org>, pgsql-patches(at)postgresql(dot)org |
Subject: | Re: [HACKERS] WITH RECURSIVE patch V0.1 |
Date: | 2008-05-19 08:42:23 |
Message-ID: | 20080519084223.GA14142@svana.org |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-hackers pgsql-patches |
On Mon, May 19, 2008 at 08:19:17AM +0200, Zoltan Boszormenyi wrote:
> >The standard has a clause to specify depth-first order. However doing a
> >depth-first traversal would necessitate quite a different looking plan and
> >it's far less obvious (to me anyways) how to do it.
>
> That would be even cooler to have it implemented as well.
From an implementation point of view, the only difference between
breadth-first and depth-first is that your tuplestore needs to be LIFO
instead of FIFO. However, just looking at the plan I don't know whether
it could support that kind of usage. At the very least I don't think
the standard tuplestore code can handle it.
> >Well, psql might wait and wait but it's actually receiving rows. A cleverer
> >client should be able to deal with infinite streams of records.
>
> I think it's the other way around. The server should not emit infinite
> number of records.
The server won't, the universe will end first. This is a nice example
of the halting problem:
http://en.wikipedia.org/wiki/Halting_problem
Which was proved unsolvable a long time ago.
Have a nice day,
--
Martijn van Oosterhout <kleptog(at)svana(dot)org> http://svana.org/kleptog/
> Please line up in a tree and maintain the heap invariant while
> boarding. Thank you for flying nlogn airlines.
From | Date | Subject | |
---|---|---|---|
Next Message | Yoshiyuki Asaba | 2008-05-19 08:57:17 | Re: WITH RECURSIVE patch V0.1 |
Previous Message | Michael Meskes | 2008-05-19 08:40:15 | Re: What in the world is happening on spoonbill? |
From | Date | Subject | |
---|---|---|---|
Next Message | Yoshiyuki Asaba | 2008-05-19 08:57:17 | Re: WITH RECURSIVE patch V0.1 |
Previous Message | Zoltan Boszormenyi | 2008-05-19 06:19:17 | Re: WITH RECURSIVE patch V0.1 |