> > 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 ---------------------------(end of broadcast)--------------------------- TIP 6: explain analyze is your friend
