Re: Updates: all or partial records

On Monday 25 January 2010 08.25:30 John R Pierce wrote:
> > My question is, which is more efficient? Performance-wise, does it
> > matter whether unchanged fields are included or omitted on UPDATE
> > statements
>
> my first order guess is, sending and having to parse the additional
> unchanged fields in your UPDATE statement is more expensive than letting
> the engine just copy them from the old tuple to the new.

Especially since setting unchanged fields might also trigger all sorts of
unneeded DB activity (check constraints, and doesn't pg now also allow
firing trigger based on which fields were updated?) which will (presumably,
don't know the code and haven't tested it) will probably not be triggered if
postgres can know that the value is not to be changed.

cheers
-- vbi

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