Re: delta relations in AFTER triggers

On Sat, Jun 28, 2014 at 07:35:10AM -0700, Kevin Grittner wrote:
> David Fetter <david(at)fetter(dot)org> wrote:
> > On Sat, Jun 21, 2014 at 11:06:26AM -0700, Kevin Grittner wrote:
>
> >> Here is v2.
>
> > I've taken the liberty of making an extension that uses this.
> > Preliminary tests indicate a 10x performance improvement over the
> > user-space hack I did that's similar in functionality.
>
> Wow, this goes well beyond what I expected for a review!  Thanks!

It was the minimum I could come up with to test whether the patch
worked.

> As I said in an earlier post, I think that this is best committed
> as a series of patches, one for the core portion and one for each
> PL which implements the ability to use the transition (delta)
> relations in AFTER triggers.

Right. I'm still holding out hope of having the transition relations
available in some more general way, but that seems more like a
refactoring job than anything fundamental.

> Your extension covers the C trigger angle, and it seems to me to be
> worth committing to contrib as a sample of how to use this feature
> in C.

It's missing a few pieces like surfacing transition table names. I'll
work on those. Also, it's not clear to me how to access the pre- and
post- relations at the same time, this being necessary for many use
cases. I guess I need to think more about how that would be done.

> It is very encouraging that you were able to use this without
> touching what I did in core, and that it runs 10x faster than the
> alternatives before the patch.

The alternative included was pretty inefficient, so there's that.

Cheers,
David.
--
David Fetter <david(at)fetter(dot)org> http://fetter.org/
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