Andrew Dunstan wrote:
>
>
> Tom Lane wrote:
> > Michael Glaesemann <
grzm@seespotcode.net> writes:
> >
> >> What would be the disadvantages of always doing this, i.e., just
> >> making this part of the normal update path in the backend?
> >>
> >
> > (1) cycles wasted to no purpose in the vast majority of cases.
> >
> > (2) visibly inconsistent behavior for apps that pay attention
> > to ctid/xmin/etc.
> >
> > (3) visibly inconsistent behavior for apps that have AFTER triggers.
> >
> > There's enough other overhead in issuing an update (network,
> > parsing/planning/etc) that a sanely coded application should try
> > to avoid issuing no-op updates anyway. The proposed trigger is
> > just a band-aid IMHO.
> >
> > I think having it as an optional trigger is a reasonable compromise.
> >
> >
> >
>
> Right. I never proposed making this the default behaviour, for all these
> good reasons.
>
> The point about making the app try to avoid no-op updates is that this
> can impose some quite considerable code complexity on the app,
> especially where the number of updated fields is large. It's fragile and
> error-prone. A simple switch that can turn a trigger on or off will be
> nicer. Syntax support for that might be even nicer, but there appears to
> be some resistance to that, so I can easily settle for the trigger.
>
> cheers
>
> andrew
>
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