Re: Return rows in input array's order?

On Tue, May 9, 2023 at 6:36 AM David Wheeler <hippysoyboy(at)gmail(dot)com> wrote:

>
> >> It was only used for small arrays but never noticed any performance
> issues
> >
> > Hmmm, sounds like this would be quadratic though...
>
> True, but it’s cpu time not io, which tends to be orders of magnitude
> slower
>
> > I wonder whether the int[] can be turned into a pseudo table with a
> ROWNUM extra generated column that
> > would then be (LEFT) JOIN'd to the accessed table, so that the original
> array index is readily accessible.
> > Would something like this be possible in Postgres' SQL?
>
> The unnest function mentioned above has a “with ordinality” option which
> gives easy access to the array index so a simple join would do the trick
>
> I've actually used this approach (array_index) for hundreds of items
without even noticing.
The other approach would be to sort your $1 list, and then just do ORDER BY
ID?