Re: defferable update & unique

Stephan Szabo wrote:
> On Wed, 19 Nov 2003, Bruce Momjian wrote:
>
> > Ben-Nes Michael wrote:
> > > Hi All
> > >
> > > Does 7.4 support defferable updates on unique column ?
> > >
> > > example
> > >
> > > unique INT colum named u_test has the following values: 1, 2, 3, 4, 5
> > >
> > > can i do update table set u_test = u_test + 1;
> >
> > No, this is on our TODO list.  Also, I can't think of a workaround.  :-(
>
> If negative values aren't allowed normally, I think you can do it in an
> ugly fashion through two updates, something like:
>
> update table set u_test=-u_test-1;
> update table set u_test=-u_test;

Excellent idea. You might want to add a VACUUM in there:

> update table set u_test=-u_test-1;
> VACUUM
> update table set u_test=-u_test;
> VACUUM

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