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Re: wCTE: about the name of the feature

From: David Fetter <david(at)fetter(dot)org>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>,Marko Tiikkaja <marko(dot)tiikkaja(at)cs(dot)helsinki(dot)fi>,pgsql-hackers(at)postgresql(dot)org
Subject: Re: wCTE: about the name of the feature
Date: 2011-02-26 22:49:44
Message-ID: 20110226224944.GA19510@fetter.org (view raw or flat)
Thread:
Lists: pgsql-hackers
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(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> > Robert Haas <robertmhaas(at)gmail(dot)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(at)fetter(dot)org> http://fetter.org/
Phone: +1 415 235 3778  AIM: dfetter666  Yahoo!: dfetter
Skype: davidfetter      XMPP: david(dot)fetter(at)gmail(dot)com
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