Ühel kenal päeval, T, 2006-07-04 kell 14:53, kirjutas Zeugswetter
Andreas DCP SD:
> > > >Is there a difference in PostgreSQL performance between these two
> > > >different strategies:
> > > >
> > > >
> > > >if(!exec("update foo set bar='blahblah' where name = 'xx'"))
> > > > exec("insert into foo(name, bar) values('xx','blahblah'"); or
>
> In pg, this strategy is generally more efficient, since a pk failing
> insert would create
> a tx abort and a heap tuple. (so in pg, I would choose the insert first
> strategy only when
> the insert succeeds most of the time (say > 95%))
>
> Note however that the above error handling is not enough, because two
> different sessions
> can still both end up trying the insert (This is true for all db systems
> when using this strategy).
I think the recommended strategy is to first try tu UPDATE, if not found
then INSERT, if primary key violation on insert, then UPDATE
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