Re: minimal update

On Fri, Mar 7, 2008 at 9:40 PM, Bruce Momjian <bruce(at)momjian(dot)us> wrote:

>
> I assume don't want a TODO for this? (Suppress UPDATE no changed
> columns)
>

I am starting to implement this. Do we want to have this trigger function in
the server, or in an external module?

Best regards,

>
>
> ---------------------------------------------------------------------------
>
> Andrew Dunstan wrote:
> >
> >
> > Tom Lane wrote:
> > > Michael Glaesemann <grzm(at)seespotcode(dot)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
> >
> > ---------------------------(end of broadcast)---------------------------
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> >
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>
> --
> Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
> EnterpriseDB http://postgres.enterprisedb.com
>
> + If your life is a hard drive, Christ can be your backup. +
>
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