On Sat, Feb 26, 2011 at 12:52:40AM -0500, Robert Haas wrote:
> On Sat, Feb 26, 2011 at 12:30 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> > Robert Haas <robertmhaas@gmail.com> writes:
> >> Yay! I'm excited about this, particularly the possible "pipelining"
> >> stuff, where you can do WITH (DELETE .. RETURNING ..) INSERT ... and
> >> have it be like cool and fast and stuff.
> >
> >> Or at least I hope you can do that.
> >
> > It's gonna need some work yet. As things stand, the tuples are indeed
> > pipelined through, but the CteScan nodes *also* stash them aside into
> > tuplestores, just in case somebody demands a rescan. Fixing that will
> > require revisiting the exec flags (EXEC_FLAG_REWIND etc). We don't
> > currently distinguish "it's unlikely you'll have to rescan" from
> > "you're guaranteed not to have to rescan", but a CteScan that's covering
> > a ModifyTable has to know the latter to not have to keep hold of copies
> > of the RETURNING tuples.
> >
> > It might be a small enough change to do after alpha starts, but I don't
> > have time for it right now.
>
> Well, if nothing else, the potential is there for a future release.
That's kinda where I am on this one. In the grand PostgreSQL
tradition, we can have something that works before we have something
that works fast :)
> I'm probably not quite as excited about this feature as David Fetter
Heh!
> (and my 100-Watt lightbulb is not quite as bright as the sun at high
> noon in midsummer) but I do think it's pretty cool, and I appreciate
> you getting it in, even in a somewhat basic form.
Me, too!
Cheers,
David.
--
David Fetter <david@fetter.org> http://fetter.org/
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