Robert Haas <robertmhaas@gmail.com> writes:
> The problems with MERGE are mostly around concurrency, as far as I can
> tell. I can't see why RULEs would have anything to do with it -
> except that I don't see how MERGE can sanely support rules, and even
> if we find a way to make it do that, anyone already using RULEs will
> need to adjust them to support MERGE. I'm not sure I have a horribly
> well-thought-out position on the underlying issue here - I'm kind of
> vacillating back and forth - but I do think one of the problems with
> RULEs is that they are too tied to particular command names. Adding
> any new commands that can select or modify data - be it MERGE, UPSERT,
> or whatever - is going to cause trouble both for implementors and for
> people relying on the feature.
And triggers (or anything else) would be better on that score because ...?
regards, tom lane