> > Is an index on a nullable column useful for retrieving rows having that
> > column null?
>
> Nope, because IS NULL isn't an indexable operator.
>
> You can make an end-run around that with a partial index, eg
>
> create index fooi on foo(f1) where f1 is null
>
> This can be used to satisfy queries using "where f1 is null", but it's
> not any good for any other purpose.
>
> If you often do "where f1 is null and something-about-f2",
> you might get better mileage with
>
> create index fooi on foo(f2) where f1 is null
>
> but it's still a very specialized index.
>
Thanks Tom. I will use such an index even if it's very specialized; OLAP world is somewhat full of specialized index
anyway...:-)
--
Daniel